Decoding method and apparatus and recording method and apparatus for moving picture data

ABSTRACT

A method and apparatus for recording moving picture data encoded using a prediction encoding system, in which the playback control information is recorded along with moving picture data encoded using the MPEG system. The playback control information includes the information specifying a program decoding starting picture and a display starting picture and the information specifying the program decoding terminating picture and a display terminating picture. During reproduction, the playback control information is first read out and moving picture data are decoded based on this information. This enables seamless reproduction from a pre-skipping picture to a post-skipping picture.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a method and apparatus for recordingmoving picture data encoded using a prediction encoding system, arecording medium having recorded thereon the moving picture data encodedusing the prediction encoding system and a method and apparatus fordecoding moving picture data encoded using the predictive encodingmethod. This invention also relates to a method and apparatus forjudging continuous reproducibility of data encoded using the predictionencoding system.

[0003] 2. Description of the Related Art

[0004] The conventional recording/reproducing apparatus for an opticaldisc generally includes an encoding unit and a decoding unit forcompanding a picture in accordance with an MPEG (Moving Picture ExpertsGroup) system. Picture signals are recorded/reproduced as the picture iscompressed or expanded using this MPEG system.

[0005] In this MPEG system, a picture constituting a moving picture(picture of a field or a frame) is encoded in accordance with a picturetype of one of I-, P- and B-pictures, by way of compressing the picture.

[0006] The I-picture is in which encoding is completed within onepicture, is encoded independently of other pictures. Thus, the I-pictureis used as an entry point for random accessing or error restoration.

[0007] The P-picture is obtained on predictive coding from a temporallypast I- or P-picture. Thus, for decoding this P-picture, the temporallypast I- or P-pictures need to be already decoded.

[0008] The B-picture is obtained on predictive coding in the forwarddirection, backward direction or in both directions from a temporallyfuture I- or P-picture. Thus, for decoding this B-picture, temporallypast and future I- or P-pictures need to be already decoded.

[0009] Thus, in the MPEG system, pictures are compressed efficiently byinter-picture predictive coding, while random accessing can be had tothe compressed moving pictures.

[0010] Also, in the MPEG system, these different sorts of pictures arecompressed into a data stream made up of an optional number of picturesgrouped together (group-of-pictures or GOP). The MPEG system providesthat at least one I-picture be present in each GOP. This renderspossible random accessing to moving pictures compressed on the GOPbasis.

[0011] It is now assumed that, in the above-described conventionalrecording/reproducing apparatus, signals compressed in accordance withthe MPEG system are to be reproduced.

[0012] On a recording medium, encoded data of a datastream shown forexample in FIG. 1 is recorded. In the conventional recording/reproducingapparatus, the datastream recorded as shown in FIG. 1A is decoded todisplay the decoded datastream in the picture sequence shown in FIG. 1B.In FIG. 1, symbols affixed to the pictures “I”, “P” and “B” denote I-,P- and B-pictures, respectively, each suffix number indicating thedisplay order in the GOP, that is the so-called temporal reference.

[0013] For reproducing the encoded data of the datastream shown in FIG.1A by the conventional recording/reproducing apparatus, a picture I₀ isdecoded first. Since the I-picture is complete in itself, theconventional recording/reproducing apparatus can decode I₀ by itselfwithout decoding other pictures. The conventional recording/reproducingapparatus then proceeds to decode forwardly predictive-coded P₂, basedon the decoded I₀. Since the P-picture is predictive-coded from thetemporally previous I- or P-picture, it is necessary for theconventional recording/reproducing apparatus to decode I₀ prior todecoding this P₂. The conventional recording/reproducing apparatus thenproceeds to decode the bidirectionally coded B₁ based on the decoded !₀and P₂. Since the B-picture is bidirectionally coded from the temporallyforward and backward I- or P-pictures, it is necessary for theconventional recording/reproducing apparatus to decode I₀ and P₂ priorto decoding this B₁. Thus, the conventional recording/reproducingapparatus decodes the encoded data of the datastream shown in FIG. 1A inthe sequence of I₀→P₂→B₁→P4→B₃→P₆→B₅→I₈→B₇→P₁₀→B₉→ . . . .

[0014] If, in the conventional recording/reproducing apparatus, thepictures decoded in the above sequence are to be displayed, the picturesequence is interchanged as shown in FIG. 1B to make a display in thesequence of I₀→B₁→P₂→B₃→P₄→B₅→P₆→B₇→I₈→B₉→P₁₀→ . . . .

[0015] Meanwhile, in the conventional recording/reproducing apparatus,if the recording medium is random-accessible, it is possible to haverandom access to the encoded data recorded by the MPEG system. Thus, itis possible with the conventional recording/reproducing apparatus toskip certain pictures by first reproducing pictures up to the P-pictureshown at S_(A) and skipping the ensuing pictures to reinitiatereproduction at the B-picture shown at a point S_(B) (picture B₃). Thisskipping of certain pictures is hereinafter termed skipping and picturereproduction from a certain picture to a different distant picture byskipping intermediate pictures is termed skip reproduction. Also, apicture directly previous to the start of the skipping, for example, apicture S_(A) shown in FIG. 2, is termed an out-point picture, while apicture at which reproduction is initiated after the end of theskipping, for example, a picture S_(B) shown in FIG. 2, is termed anin-point picture.

[0016] However, if this skip reproduction is performed on theconventional recording/reproducing apparatus, there are occasionswherein temporal continuity of reproduced pictures is interrupted andlost.

[0017] If, for example, the in-point picture is a B-picture, it isnecessary to previously decode an I- or a P-picture required fordecoding this B-picture, in which case temporal continuity of reproducedpictures is interrupted and lost. More specifically, with reference toan instance shown in FIG. 2, since the in-point picture is B₃ with theconventional recording/reproducing apparatus, at least I₀, P₂ and P₄need to be decoded in order to decode this B₃. Thus, with theconventional recording/reproducing apparatus, no picture can bedisplayed while I₀, P₂ and P₄ are decoded, such that the picturecontinuity is interrupted and lost.

[0018] As described above, it is not possible with the conventionalrecording/reproducing apparatus to achieve seamless reproduction ofpictures ahead and at back of skipping on the occasion of skippingreproduction.

[0019] Although the above example is pertinent to picture compression inaccordance with the MPEG system, temporal continuity in skippingreproduction is similarly interrupted and lost even in case ofinter-picture predictive coding in which the difference between picturesis found in order to exploit the inter-picture correlation and thedifference thus found is encoded.

SUMMARY OF THE INVENTION

[0020] It is therefore an object of the present invention to provide adecoding method and apparatus for decoding moving picture data in whichcontinuity of moving pictures before and after the skipping ismaintained to enable skipping reproduction.

[0021] It is another object of the present invention to provide arecording method and apparatus for recording moving pictures in such amanner that a reproduction starting picture and a reproductiontermination picture can be decoded and outputted correctly at the thineof reproducing moving picture data, and that, at the time of skippingreproduction, skipping from the reproduction termination picture to thereproduction starting picture can be effected seamlessly.

[0022] It is a further object of the present invention to provide arecording medium on which moving picture data are recorded thereon sothat the reproduction starting picture and the reproduction terminationpicture can be correctly decoded and outputted at the time ofreproducing moving picture data, and so that, at the time of skippingreproduction, skipping from the reproduction termination picture to thereproduction starting picture can be effected seamlessly.

[0023] It is a further object of the present invention to provide amethod and apparatus for decoding moving picture data so that thereproduction starting picture and the reproduction termination picturecan be decoded and outputted correctly and so that, at the time ofskipping reproduction, skipping from the reproduction terminationpicture to the reproduction starting picture can be effected seamlessly.

[0024] It is yet another object of the present invention to provide amethod and apparatus for judging feasibility of continuous reproductionof moving picture data at the time of skipping reproduction.

[0025] In one aspect, the present invention provides a decodingapparatus for data of moving pictures for decoding encoded data ofmoving pictures encoded using a predictive encoding system, includingdecoding means for decoding first encoded data made up of movingpictures up to a preset moving picture and second encoded data made upof moving pictures beginning from a moving picture displayed next to thepreset moving picture at a speed faster than the display speed of theencoded data, and output control means for controlling the outputting ofdecoded moving pictures based on the time management information of eachmoving picture of the encoded data.

[0026] With the decoding apparatus for multiplexed data according to thepresent invention, the decoding means time-divisionally decoding thefirst encoded data and the second encoded data.

[0027] Also, with the decoding apparatus for multiplexed data accordingto the present invention, there is provided storage means fortemporarily storing decoded moving picture data.

[0028] With the present moving picture data decoding apparatus, thefirst encoded data and the second encoded data are decoded at a decodingspeed faster than the display speed.

[0029] In another aspect, the present invention provides a decodingmethod for data of moving pictures for decoding encoded data of movingpictures encoded using a predictive encoding system including a decodingstep for decoding first encoded data made up of moving pictures up to apreset moving picture and second encoded data made up of moving picturesbeginning from a moving picture displayed next to the preset movingpicture at a speed faster than the display speed of the encoded data,and an output control step for controlling the outputting of decodedmoving pictures based on the time management information of each movingpicture of the encoded data.

[0030] In the present moving picture data decoding method, the decodingstep time-divisionally decodes the first and second encoded data duringthe decoding step.

[0031] In the present moving picture data decoding method, there isprovided a storage step for temporarily storing decoded moving picturedata.

[0032] In the present moving picture data decoding method, the first andsecond encoded data are decoded at a decoding speed higher than thedisplay speed.

[0033] In a further aspect, the present invention provides a decodingapparatus for data of moving picture for decoding encoded data of movingpictures encoded using a predictive encoding system, including firstdecoding means for decoding encoded data up to a moving picture whosedisplay is completed at a first time point corresponding to a presetdisplay time point, second decoding means for decoding encoded databeginning from a moving picture which starts to be displayed at a secondtime point skipped a preset time interval from the first time point,output control means for controlling the outputting of a moving picturedecoded by the first decoding means or the second decoding means whenthe time management information of the encoded data coincides withreference synchronization signals, and switching means for changing thereference synchronization signals to the second time point when thereference synchronization signals are equal to the first time point forswitching the moving picture output-controlled by the output controlmeans to the picture decoded by the second decoding means.

[0034] In the present moving picture data decoding apparatus, a picturedecoded by the first decoding means and whose display is terminated at afirst time point and a picture decoded by the second decoding means andwhose display is started at a second time point are switched andoutputted simultaneously with switching of the reference synchronizationsignal.

[0035] In a further aspect, the present invention provides a decodingmethod for data of moving picture for decoding encoded data of movingpictures encoded using a predictive encoding system, including a firstdecoding step for decoding encoded data up to a moving picture whosedisplay is completed at a first time point corresponding to a presetdisplay time point, a second decoding step for decoding encoded databeginning from a moving picture which starts to be displayed at a secondtime point skipped a preset time interval from the first time point, anoutput control step for generating a reference synchronization signaland for controlling the outputting of a moving picture decoded by thefirst decoding step or the second decoding step when the time managementinformation coincides with reference synchronization signals and aswitching step for changing the reference synchronization signal to thesecond time point when the reference synchronization signal is equal tothe first time point for switching the moving picture output-controlledby the output control step to the picture decoded by the second decodingstep.

[0036] In the present moving picture data decoding method, a picturedecoded by the first decoding means and whose display is terminated at afirst time point and a picture decoded by the second decoding means andwhose display is started at a second time point are switched andoutputted simultaneously with switching of the reference synchronizationsignal.

[0037] In a further aspect, the present invention provides a recordingapparatus for moving picture data including encoding means for encodingmoving picture data using a predictive encoding system, designationinformation supplying means for supplying the information designating adecoding starting picture and a display starting picture in the movingpicture data and for supplying the information designating a decodingterminating picture and a display terminating picture in the movingpicture data and recording means for recording moving picture dataencoded by the encoding means and the designation information suppliedby the designation information supplying means.

[0038] In the present moving picture data recording apparatus, theinformation specifying a decoding starting picture and a displaystarting picture in moving picture data and the information specifyingthe decoding terminating picture and the display terminating picture inthe moving picture data are recorded on the recording medium.

[0039] In a further aspect, the present invention provides a recordingmethod for moving picture data including encoding means for encodingmoving picture data using a predictive encoding system, supplying theinformation designating a decoding starting picture and a displaystarting picture in the moving picture data and for supplying theinformation designating a decoding terminating picture and a displayterminating picture in the moving picture data, and recording encodedmoving picture data and the supplied designation information.

[0040] In the present moving picture data recording method, theinformation specifying a decoding starting picture and a displaystarting picture in moving picture data and the information specifyingthe decoding terminating picture and the display terminating picture inthe moving picture data are recorded on the recording medium.

[0041] In a further aspect, the present invention provides a recordingmedium on which there are recorded the information designating adecoding starting picture and a display starting picture in movingpicture data and the information designating a decoding terminatingpicture and a display terminating picture in moving picture data alongwith encoded data of moving pictures encoded using the predictiveencoding system.

[0042] On the present recording medium, there are recorded theinformation specifying a decoding starting picture and a displaystarting picture in moving picture data and the information specifyingthe decoding terminating picture and the display terminating picture inthe moving picture data.

[0043] In a further aspect, the present invention provides a decodingapparatus for moving picture data including decoding means for decodingencoded data of moving pictures encodedusing a predictive encodingsystem, and control means for controlling the decoding and theoutputting of moving picture data by the decoding means based on theinformation designating a decoding start picture and a display startpicture in moving picture data and on the information designating adecoding terminating picture and a display terminating picture in themoving picture data.

[0044] In the present moving picture data decoding apparatus, encodeddata of a moving picture encoded using the inter-picture predictiveencoding system are decoded based on the information specifying thedecoding starting picture and the display starting picture in movingpicture data and on the information specifying the decoding terminatingpicture and the display terminating picture in the moving picture dataand the decoded data are outputted.

[0045] In a further aspect, the present invention provides a decodingmethod for moving picture data including decoding encoded data of amoving picture encoded using a predictive encoding system based on theinformation specifying a decoding starting picture and a displaystarting picture in moving picture data and on the informationspecifying a decoding terminating picture and a display terminatingpicture in moving picture data, and outputting the decoded data.

[0046] In the present moving picture data decoding method, encoded dataof a moving picture encoded using the inter-picture predictive encodingsystem are decoded based on the information specifying the decodingstarting picture and the display starting picture in moving picture dataand on the information specifying the decoding terminating picture andthe display terminating picture in the moving picture data and thedecoded data are outputted.

[0047] In yet another aspect, the present invention provides acontinuous reproduction possibility verifying method and apparatus forencoded data wherein, in reproducing a series of encoded data encodedusing a predictive encoding system by decoding pictures of the encodeddata from a first display starting point picture of the encoded data toa first display terminating point picture of the encoded data,designated as an out-point picture in skipping processing of the encodeddata, then skipping the decoding from the first display terminatingpoint picture to a second display starting point picture designated asan in-point picture in the skipping processing, and by decoding picturesfrom the second display starting point picture to a second displayterminating point picture, it is verified, based on the time differencebetween a display time point of the first display starting point pictureand a display time point of the first display terminating point picture,whether or not continuous display of the first display terminating pointpicture and the second display starting point picture is possible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0048]FIG. 1 illustrates pictures encoded in accordance with the MPEGsystem.

[0049]FIG. 2 illustrates skipping reproduction of encoded data encodedin accordance with the MPEG system.

[0050]FIG. 3 is a block diagram of an optical disc recording/reproducingapparatus according to a first embodiment of the present invention.

[0051]FIG. 4 illustrates the relation between an out-point side programand an in-point side program at the time of skipping reproduction.

[0052]FIG. 5 shows the reproduction route for an AV program at the timeof skipping reproduction for illustrating the relation between thedisplay end time of the out-point side program (PTS_Pout_end) ) and thedisplay start time of the in-point side program (PTS_Pin) .

[0053]FIG. 6 shows the relation between the multiplexed stream of the AVprogram file containing the in-point side program and the byte addressof the multiplexed stream.

[0054]FIG. 7 shows the relation between the multiplexed stream of the AVprogram file containing the out-point side program and the byte addressof the multiplexed stream.

[0055]FIG. 8 shows the relation between the byte address of amultiplexed stream recorded on an optical disc on one hand and thedecoding starting position (decode_start_address) and the decoding endposition (decode_end_address) of a certain AV program.

[0056]FIG. 9 shows an illustrative description of an AV program filerecorded on an optical disc.

[0057]FIG. 10 shows an illustrative description of the reproductioncontrol in recorded on an optical disc.

[0058]FIG. 11 is a block diagram of a decoding device of arecording/reproducing apparatus according to the first embodiment of thepresent invention.

[0059]FIG. 12 is a flowchart showing decoding and outputting processingof a decoding device of an optical disc recording and/or reproducingapparatus according to the first embodiment of the present invention.

[0060]FIG. 13 is a flowchart, consecutive to FIG. 12, for decoding andoutputting processing of a decoding device of an optical disc recordingand/or reproducing apparatus according to the first embodiment for acase in which seamless reproduction is possible.

[0061]FIG. 14 is a flowchart, consecutive to FIG. 12, for decoding andoutputting processing of a decoding device of an optical disc recordingand/or reproducing apparatus according to the first embodiment for acase in which seamless reproduction is not possible.

[0062]FIG. 15A illustrates an example of the picture sequence of theout-point side program and the in-point side program for illustratingthe decoding and display timing of the decoding device of the opticaldisc recording and/or reproducing apparatus according to the firstembodiment.

[0063]FIG. 15B shows the decoding timing of the out-point side programshown in FIG. 15A.

[0064]FIG. 15C shows the display timing of the in-point side programshown in FIG. 15A.

[0065]FIG. 15D shows the decoding timing of the in-point side programshown in FIG. 15A.

[0066]FIG. 15E shows the display timing of the in-point side programshown in FIG. 15A.

[0067]FIG. 15F shows the display timing of the out-point side programand the in-point side program shown in FIG. 15A.

[0068]FIG. 16A illustrates the amount of bits occupying a main buffer ofthe decoding device of the recording/reproducing apparatus of an opticaldisc of the first embodiment of the present invention.

[0069]FIG. 16B illustrates the amount of bits occupying a first videobuffer of the decoding device of the recording/reproducing apparatus ofan optical disc of the first embodiment of the present invention.

[0070]FIG. 16C illustrates the amount of bits occupying a second videobuffer of the decoding device of the recording/reproducing apparatus ofan optical disc of the first embodiment of the present invention.

[0071]FIG. 17 is a block diagram of a decoding device of the opticaldisc recording/reproducing apparatus according to a second embodiment ofthe present invention.

[0072]FIG. 18 is a block diagram of a video decoding portion of thedecoding device of the optical disc recording/reproducing apparatusaccording to the second embodiment of the present invention.

[0073]FIG. 19 is a flowchart showing decoding and outputting processingof the decoding device of the optical disc recording/reproducingapparatus according to the second embodiment of the present invention.

[0074]FIG. 20 is a flowchart consecutive to FIG. 19 for illustrating thedecoding and outputting processing of the decoding device of thedecoding device of the optical disc recording/reproducing apparatusaccording to the second embodiment of the present invention in caseseamless reproduction is possible.

[0075]FIG. 21 is a flowchart consecutive to FIG. 19 for illustrating thedecoding and outputting processing of the decoding device of thedecoding device of the optical disc recording/reproducing apparatusaccording to the second embodiment of the present invention in caseseamless reproduction is not possible.

[0076]FIG. 22A illustrates an instance of picture sequence of theout-point side program and the in-point side program for illustratingthe decoding and display timing of the optical discrecording/reproducing apparatus according to the first embodiment of thepresent invention.

[0077]FIG. 22B shows the decoding timing of the out-point side programshown in FIG. 22A.

[0078]FIG. 22C shows the display timing of the out-point side programshown in FIG. 22A.

[0079]FIG. 22D shows the decoding timing of the in-point side programshown in FIG. 22A.

[0080]FIG. 22E shows the display timing of the in-point side programshown in FIG. 22A.

[0081]FIG. 22F shows the display timing of the out-point side programand the in-point side program shown in FIG. 22A.

[0082]FIG. 23A illustrates the amount of bits occupying a main buffer ofthe decoding device of the recording/reproducing apparatus of an opticaldisc of the second embodiment of the present invention.

[0083]FIG. 23B illustrates the amount of bits occupying the first videobuffer of the decoding device of the recording/reproducing apparatus ofan optical disc of the second embodiment of the present invention.

[0084]FIG. 23C illustrates the amount of bits occupying the second videobuffer of the decoding device of the recording/reproducing apparatus ofan optical disc of the second embodiment of the present invention.

[0085]FIG. 24 is a block diagram of a decoding device of the opticaldisc recording/reproducing apparatus according to a third embodiment ofthe present invention.

[0086]FIG. 25 is a flowchart showing data reading processing into themain buffer of the decoding device of the optical discrecording/reproducing apparatus according to the third embodiment of thepresent invention.

[0087]FIG. 26 is a flowchart consecutive to FIG. 19 for illustrating thedecoding and outputting processing of the decoding device of thedecoding device of the optical disc recording/reproducing apparatusaccording to the third embodiment of the present invention in caseseamless reproduction is possible.

[0088]FIG. 27 is a flowchart consecutive to FIG. 26 for illustrating thedecoding and outputting processing of the decoding device of the opticaldisc recording/reproducing apparatus according to the third embodimentof the present invention.

[0089]FIG. 28A illustrates an instance of picture sequence of anout-point side program and an in-point side program for illustrating thedecoding timing and the display timing of the decoding device of theoptical disc recording/reproducing apparatus according to the thirdembodiment of the present invention.

[0090]FIG. 28B shows the decoding timing of the out-point side programshown in FIG. 28A.

[0091]FIG. 28C shows the display timing of the out-point side programshown in FIG. 28A.

[0092]FIG. 28D shows the decoding timing of the in-point side programshown in FIG. 28A.

[0093]FIG. 28E shows the display timing of the in-point side programshown in FIG. 28A.

[0094]FIG. 28F shows the display timing of the out-point side programand the out-point side program shown in FIG. 28A.

[0095]FIG. 29A shows the amount of bits occupying a main buffer of thedecoding device of the recording/reproducing apparatus of an opticaldisc of the third embodiment of the present invention.

[0096]FIG. 29B shows the amount of bits occupying a video buffer of thedecoding device of the recording/reproducing apparatus of an opticaldisc of the third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0097] Referring to the drawings, preferred embodiments of an opticaldisc recording/reproducing apparatus embodying the present inventionwill be explained in detail.

First Embodiment

[0098] First, a recording/reproducing apparatus according to a firstembodiment of the present invention will be explained.

[0099]FIG. 3 shows a block diagram of an optical discrecording/reproducing apparatus embodying the present invention.

[0100] An an optical disc recording/reproducing apparatus 1 reproducesvideo and audio data, encoded for signal compression in accordance withthe MPEG 2 (Moving Picture Exerts Group 2) system from arandom-accessible optical disc 2, and encodes video and audio data on arandom-accessible optical disc 2 in accordance with the MPEG 2 system torecord the encoded data on the optical disc 2.

[0101] The recording/reproducing apparatus 1 includes a readout unit 3for reading out video data, audio data and the playback controlinformation compressed by the MPEG system and recorded in thiscompressed form on the optical disc 2, a demodulating unit 4 fordemodulating the read-out video data, audio data and the playbackcontrol information, an error correction and coding unit 5 forcorrecting the video data, audio data and the playback controlinformation for errors based on the error correction code, and a buffer6 for transiently storing the error-corrected video and audio data. Theoptical disc recording/reproducing apparatus 1 also includes a playbackcontrol information memory 7 for storage of the read-out playbackcontrol information, a playback controller 8 for controlling the readoutunit 3 in accordance with the playback control information to controlthe reproduction of the optical disc 2 and a decoding device 10 fordecoding the read-out video and audio data. The optical discrecording/reproducing apparatus 1 also includes a an operating inputunit 11, fed with the operating input information from a user, aplayback control information encoding unit 12 for encoding the video andaudio data recorded on the optical disc 2 and an error correction codedevice 13 for encoding the video and audio data in accordance with MPEGsystem. The optical disc recording/reproducing apparatus 1 also includesan error correction code appendage unit 14 for appending the errorcorrection code to the encoded video data, audio data and the playbackcontrol information and a demodulation unit 15 for demodulating thevideo data, audio data and playback control information to which hasbeen appended the error correction code. The optical discrecording/reproducing apparatus 1 further includes a writing unit 16 forwriting on the optical disc 2 the modulated video data, audio data andplayback control information, and a decision information display unit 17for displaying the discriminating information as discriminated by theplayback controller 8.

[0102] When encoding the input video and audio data in accordance withthe MPEG system and recording the encoded data on the optical disc 2,the optical disc recording/reproducing apparatus 1 executes thefollowing processing:

[0103] First, uncompressed video and audio data are entered from anexternal device to an encoding device 13. The encoding device 13 encodesthe input video and audio data in accordance with MPEG 2 system for datacompression. The encoded video data and the encoded audio data arepackaged independently of each other. This encoding device 13multiplexes the packaged video and audio data to send the multiplexeddata to the error correction code appendage unit 14. The errorcorrection code appendage unit 14 appends an error correction code tothe video and audio data entered from the encoding device 13 to send theresulting data to the modulation unit 15. The modulation unit 15modulates the video and audio data entered form the error correctioncode appendage unit 14 to send the resulting data to the writing unit16, which then records the video and audio data entered from themodulation unit 15 on the optical disc 2.

[0104] When reproducing the video and audio data recorded on the opticaldisc 2, the optical disc recording/reproducing apparatus 1 executes thefollowing processing. It is noted that the present optical discrecording/reproducing apparatus 1 reproduces video and audio datarecorded on the optical disc 2 in terms of an AV program as a series ofdata reproducing units from a pre-set playback start point up to apre-set playback end point.

[0105] First, the readout unit 3 reads out from the optical disc 2 theplayback control information specifying the control information on thedecoding and display of the AV program and on the readout of the AVprogram to send the read-out information to the demodulating unit 4,which then demodulates the playback control information entered from thereadout unit 3 to send the demodulated information to the errorcorrection and coding unit 5. The error correction and coding unit 5corrects the playback control information sent from the readout unit 3for errors to store the error-corrected playback control information inthe memory 7. The operating input unit 11 is responsive to the operatinginput by the user to generate the control information specifying theplayback sequence or the reproducing route of the AV program to send thegenerated control information to the playback controller 8. The playbackcontroller 8 then retrieves the playback control information of thereproduced AV program, responsive to the operating input by a user, tosend the playback control information of the reproduced AV program tothe playback controller 8. The playback controller 8 then controls thereadout unit 3 responsive to the retrieved playback control informationto start reproduction of the video and audio data based on the retrievedplayback control information on the AV program basis and sends theretrieved playback control information to the decoding device 10.

[0106] When the playback operation is started on the AV program basis,the readout unit 3 reads out the video and audio data, recorded on theoptical disc 2 after compression encoding by the MPEG system 2, undercontrol by the playback controller 8. The video and audio data, read outat this time, are formed into packages and multiplexed on the packagebasis. The demodulating unit 4 demodulates the video and audio data,entered from the readout unit 3, to send the demodulated data to theerror correction and coding unit 5. The error correction and coding unit5 corrects the video and audio data, entered from the demodulating unit4, for errors, and sends the error-corrected data to the buffer 6. Thebuffer 6 transiently stores the furnished video and audio data. At thistime, the playback controller 8 monitors the data storage quantity ofthe buffer 6 and performs control to read out data from the optical disc2 as long as there is any available vacant area in the buffer 6. Thebuffer 6 sends the video and audio data stored therein to the decodingdevice 10. This buffer 6 absorbs the readout interrupt time caused byreadout errors during the pickup movement time or until the servo stateis restored to the steady state in order to supply the video and audiodata to the decoding device 10 as a continuous stream. The decodingdevice 10 decodes the video and audio data to output the decoded videand audio data to outside.

[0107] If the AV program recorded on the optical disc 2 is edited tochange the reproduction starting point or the reproduction terminationpoint for the video or audio data, the playback sequence of the AVprogram is changed or the new AV program is formulated, theabove-described optical disc recording/reproducing apparatus 1 executesthe following processing:

[0108] First, to the operating input unit 11 are entered thereproduction starting point and the reproduction termination point ofthe new AV program responsive to the editing operation by the user. Theplayback controller 8 reads out from the optical disc 2 data requiredfor reproducing and decoding the new AV program and for reading out thenew AV program, based on the above information entered responsive to theediting actuation by the user, and causes the read-out data to be storedin the playback control information memory 7. The playback controlinformation encoding unit 12 generates the playback control informationfor the new AV program based on the data stored in the playback controlinformation memory 7. An error correction code is appended to theplayback control information by the error correction code appendage unit14. The resulting data is modulated by the modulation unit 15 so as tobe recorded on the optical disc 2.

[0109] The processing during skipping reproduction of therecording/reproducing application programs for the optical disc is nowexplained.

[0110] The AV program containing an out-point picture Pout duringskipping reproduction is termed an out-point side program. A picture onthe out-point side program decoded last during skipping reproduction istermed the last picture Plast. The AV program containing the in-pointpicture Pin during skipping reproduction is termed an in-point sideprogram. The first picture on the in-point side program decoded firstduring skipping reproduction is termed a leading picture Pfirst.

[0111] The out-point side program and the in-point side program areexplained specifically with reference to FIG. 4. If, for example, B₀₇ ofa GOP-0 is an out-point picture Pout, B₀₇ of a GOP-0 represents the lastpicture Plast, with data up to this B₀₇ representing the out-point sideprogram. Similarly, if P₀₇ of GOP-n, skipped from B₀₇ of GOP-0, is anin-point picture Pin, I_(n2) of the GOP-n is the leading picture Pfirst,with data downstream of I_(n2) representing the in-point side program.The i'th GOP in the display sequence is specified as GOP-i. Also, anj'th I-picture of the i'th GOP in the display sequence is specified asIij, and a j'th P-picture in the display sequence of the i'th GOP isspecified as Pij, while the j'th B-picture in the display sequence isspecified as Bij.

[0112] If skipping reproduction is to be performed by the optical discrecording/reproducing apparatus 1, the playback control information,such as the out-point side program or the in-point side program, areentered from outside, responsive to the actuating input by the user.Alternatively, the playback control information pre-recorded on theoptical disc 2, such as the out-point side program or the in-point sideprogram, is read out and sent to the playback controller 8. The playbackcontroller 8 controls the readout unit 3, based on the playback controlinformation of the out-point side program and the in-point side program,and sends the playback control information of the out-point side programand the in-point side program to the decoding device 10.

[0113] In the playback control information, there are contained theinformation required for controlling the decoding and display of the AVprogram, and the control information for reading out the AV program fromthe optical disc 2. The playback controller 8 sends to the decodingdevice 10 the portion of the playback control information that isrequired for controlling the decoding and display of the AV program. Theplayback controller 8 also sends the portion of the playback controlinformation that is required for reading out the AV program from theoptical disc 2 to the readout unit 3.

[0114] In the playback control information, there are contained, as theinformation required for controlling the decoding and display of the AVprogram, the following information items:

[0115] P_last_index: Position information of the last picture Plast (thepicture position information is sometimes referred to hereinafter asindex).

[0116] The picture index can be represented for example by the displaysequence of the GOP containing the picture and the display sequence ofthe picture in the GOP. In an example shown in FIG. 4, for example, theindex of the last picture Plast is specified by the display sequence ofthe GOP containing B₀₇ and temporal_reference of B₀₇. That is, in theexample shown in FIG. 4, the index of the last picture Plast is “07”.Meanwhile, temporal_reference specifies the display sequence of thepicture in the GOP by a number.

[0117] P_in_index: Position information of the in-point picture Pin

[0118] The index of the in-point picture Pin is represented in theexample shown in FIG. 4 by, for example, the display sequence of the GOPcontaining P_(n5) and temporal_reference of this P_(n5). That is, in theexample shown in FIG. 4, the index of the in-point picture Pin is “n5”.

[0119] P_in_type: Picture type of the in-point picture Pin

[0120] In the example shown in FIG. 4, for example, the picture type ofthe in-point picture Pin is a P-picture.

[0121] P_out_last_field_parity: Parity of the field represented at thetrailing end of the out-point picture Pout

[0122] The parity of this field is the information provided inconsideration of 2-3 pull-down provided in MPEG 2 system ( forcorrecting the number of frames per second between the televisionbroadcasting and cinema).

[0123] P_in_first_field_parity: Parity of the field represented first inthe in-point picture Pin

[0124] PTS_Pin: A value corresponding to PTS of the out-point picturePout added to with the display time of the out-point picture Pout, thatis the PTS of the time point of termination of display of the out-pointpicture Pout (this is sometimes referred to hereinafter as PTS_Pout_end)).

[0125] The playback control information required for controlling thedecoding and display of the AV program is read out from the optical disc2 by the playback controller 8 and subsequently sent to the decodingdevice 10.

[0126] In the playback control information, there are contained, as theinformation required in reading out the AV program from the optical disc2, the following information items:

[0127] decode_start_address: An address of initial data required forreproducing the AV program beginning at a time point indicated by PTS ofthe in-point picture Pin (PTS_Pin)

[0128] For example, this information item is the address of the firstbyte of the in-point side program on the optical disc 2 (byte offsetfrom the leading end of the file of the AV program containing thein-point side program up to the first byte of the in-point sideprogram).

[0129] decode_end_address: An address specifying last data required forreproducing the AV program up to a time point PTS_Pout_end.

[0130] For example, this information item is an address of the last byteof the out-point side program on the optical disc 2 (byte offset fromthe leading end of the file of the AV program file containing theout-point side program up to the last byte of the out-point sideprogram).

[0131] The playback control information, required for controlling thereadout of the AV program, is read out from the optical disc 2 by theplayback controller 8 and sent as the readout control information to thereadout unit 3.

[0132] The recording/reproducing apparatus 1 for the optical disc canread out data up to the out-point picture Pout of the out-point sideprogram from the optical disc 2, by using the playback controlinformation specifying the above contents in performing the skippingreproduction, while it can read out data from in-point picture Pin ofthe in-point side program from the optical disc 2.

[0133] Also, the optical disc recording/reproducing apparatus canspecify a picture denoting the decoding end based on decode_end_addressof the playback control information, and also can specie a picturedenoting the end of display based on PTS_Pout_end of the playbackcontrol information, so that the decoding and display of the out-pointside program can be performed correctly at the time of skippingreproduction. That is, decoding of the out-point side program isperformed up to B₀₇, as the last picture Plast, in the example shown inFIG. 4, by employing the playback control information. However, sincethe out-point picture Pout, displayed last, is B₀₇, control can beperformed so that decoded P₀₈ will not be displayed.

[0134] On the other hand, the recording/reproducing apparatus for theoptical disc 1 can specify a picture denoting the decoding start, basedon decode start address of the playback control information, and alsocan specify a picture denoting start of display, based on PTS_Pin of theplayback control information, so that the in-point side program can bedecoded and displayed correctly during skipping reproduction. That is,the decoding of the in-point side program is started from I_(n2) as theleading picture Pfirst, in the example shown in FIG. 4, by employing theplayback control information. However, since the in-point picture Pindisplayed first is P₅, control can be performed so that decoded I_(n2)will not be displayed.

[0135] The relation between PTS_Pout_end of the out-point side programand PTS_Pin of the in-point side program during skipping reproduction isnow explained. FIG. 5 shows the reproduction route in case video andaudio data are sequentially reproduced across three AV programs of fromAV program-1 to AV program-3.

[0136] In the AV programs of from AV program-1 to AV program-3, PTS_Pinand PTS_Pout_end are specified by the playback control information, andthe respective programs are read out from the optical disc 2 based onPTS_Pin and PTS_P out. First, the AV program 1, as an AV program to bereproduced first, is read out from the optical disc 2, and is reproducedfrom the in-point picture started to be displayed at a time point PTS_Pin (1) up to the out-point picture whose display is completed at a timepoint PTS_Pout_end (1). Reproduction is skipped from an out-pointpicture, whose display is completed at this time point PTS_Pout_end (1).The AV program-2, which is an AV program to be reproduced next, is readout from the optical disc 2, and reproduction proceeds from an in-pointpicture, which starts to be displayed at a time point PTS_Pout_end (2),up to an out-point picture whose display is completed at a time pointPTS_Pout_end (2). Reproduction is skipped from an out-point picture,whose display is completed at this time point PTS_Pout_end (2). The AVprogram-3, which is an AV program to be reproduced next, is read outfrom the optical disc 2, and reproduction proceeds from an in-pointpicture, which starts to be displayed at a time point PTS_Pout_end (3),up to an out-point picture whose display is completed at a time pointPTS_Pout end (3).

[0137] It is noted that, in case of this skipping reproduction from theAV program-1 to the AV program-2, PTS_Pout_end (1), which is the displayend time of the out-point picture of the AV program-1 , is coincident inreal-time with PTS_Pin (2), which is the display start time point of thein-point picture of the AV program-2. Similarly, in case of the skippingreproduction from the AV program-2 to the AV program-3, PTS_Pout_end(2), which is the display end time of the out-point picture of the AVprogram-2, is coincident in real-time with PTS_Pin (3), which is thedisplay start time point of the in-point picture of the AV program-3.Thus, when the system time clock (STC), which manages the picturedecoding timing and the picture display timing, is the display end timeof the out-point picture, the display start time is switched to thedisplay start time of the in-point picture of the next program. Forexample, if STC is PTS_Pout_end (1), an offset STC_offset (1) issubtracted from this STC to switch the display start time to PTS_in (2).Also, if STC is PTS_Pout_end (2), an offset STC_offset (2) is subtractedfrom this STC to switch the display start time to PTS_in (2). Meanwhile,this offset is obtained on subtraction of PTS_Pout_end indicated in theplayback control information of the out-point side program and PTS_Pinindicated in the playback control information of the in-point sideprogram.

[0138] By switching the system time clock (STC) during skippingreproduction from PTS_Pout_end indicated in the playback controlinformation of the out-point side program to PTS_Pin indicated in theplayback control information of the in-point side program, it ispossible to perform seamless reproduction of plural AV programs.

[0139] By the editing by the user of the reproducing route of the AVprograms recorded on the optical disc 2, new reproducing routes can beprepared. The information on the reproducing routes is generated by theplayback control information encoding unit 12 responsive to an actuatinginput by the user and recorded on the optical disc 2 as the ancillaryinformation for the AV program. By preparing the new reproducing routesin this manner, the reproducing routes can be easily re-edited withoutdecoding and re-encoding video and audio data.

[0140] The relation between a multiplexed stream recorded on the opticaldisc 2 on one hand and decode_start_address and decode_end_address onthe AV program is explained. FIGS. 6 and 7 illustrate the relationbetween a multiplexed stream of an AV program file containing thein-point side program and byte addresses of the multiplexed stream andthat between a multiplexed stream of an AV program file containing theout-point side program and byte addresses of the multiplexed stream. InFIGS. 6 and 7, the abscissa denotes the addresses in the AV programfile.

[0141] Referring to FIG. 6, decode_start_address shown in the playbackcontrol information of the in-point side program can be specified foreach of the video data and the audio data. It is noted thatdecode_start_address is shown as an offset quantity fromfirst_byte_address as a leading-end address of an AV program filecontaining the in-point side program. Therefore, the package (pack 1) ata position of video_decode_start_address of video data represents thefirst package containing data of the leading-end picture Pfirst (In2 inthe drawing) of the in-point side program. Pictures downstream of theleading-end picture of the in-point side program are stored in packagesdownstream of the package (pack 1) at this video_decode_start_address.For example, the in-point picture Pin (I_(n5) in the drawing) is storedas from the package which is five packages ahead (pack 2). The package(pack 3) at audio decode start_address specifying decode_start_addressof the audio data is the package containing the audio data reproduced atthe display start timing (PTS_Pin) of the in-point picture Pin.Meanwhile, suffix subscripts (n4, n5 and so forth) specifying audio datain the drawing (indicated A in the drawing) indicate that the data inquestion is reproduced in synchronism with the picture specified by thesuffix subscript bearing the same number. Meanwhile, since audio dataare not subjected to predictive coding, in contradistinction frompicture data, it is decoded from data specified in decode_start_addressand outputted.

[0142] The decode_end_address, indicated in the playback controlinformation of the out-point side program, can be specified by each ofthe video data and the audio data, as shown in FIG. 7. Thedecode_end_address is indicated by, for example, an offset from thefirst_byte_address which is the leading end address of the AV programfile containing the out-point side program. Thus, the package at aposition of video_decode_end_address, specifying decode_end_address ofvideo data, represents the last package containing data of the lastpicture Plast (B07 in the drawing) of the out-point side program. Sincethe last picture Plast of the out-point side program coincides with theout-point picture Pout, data of the out-point picture Pout is stored upto the package (pack 5) at a position of video_decode_end_address. Also,a package (pack 6) at a position of audio_decode_end_address specifyingthe decode_end_address of the audio data represents a package containingaudio data reproduced at a display end time (PTS_Pout end) of theout-point picture Pout.

[0143]FIG. 8 shows the relation between the byte address of themultiplexed stream recorded on the optical disc 2 on one hand and thedecode_start_address and the decode_end_address of a certain AV programon the other hand. The abscissa in FIG. 8 stands for addresses in the AVprogram file.

[0144] An AV program is prescribed from a series of video data fromvideo_decode_start_address to video_decode_end_address and from a seriesof audio data from audio_decode_start_address to audio_decode_addressassociated with the series of video data. The video and audio datarecorded on the optical disc 2 are reproduced on the AV program basis.

[0145] Each package constituting the multiplexed stream recorded on theoptical disc 2 is stored in the AV program file. In the AV program file,a loop- is formed by a “do˜while” sentence, as shown in FIG. 9. In a“pack” stated in this “do˜while” sentence are described “package_header”and “PES_packet”. In the “PES_packet” are stated “pack_header”, “PTS”,“DTS” and “packet_payload”. In this “packet_payload” are stored videodata or audio data.

[0146] On the optical disc 2 are recorded, along with the AV programfile, the playback control information file (playback_information_file),stating the playback control information, as shown in FIG. 10. Thisplayback control information file is recorded from one AV program toanother. That is, a sole item of the playback control information isrecorded for each AV program.

[0147] By recording the AV program file and the playback controlinformation on the optical disc 2 and by reading out the AV program fileand the playback control information from the optical disc 2, it ispossible to read out plural AV programs to reproduce the read-outprogram by seamless skipping reproduction.

[0148] By the user newly formulating the playback control informationfile or changing the existing playback control information, it ispossible to formulate a new AV program to edit the video program alreadyrecorded on the optical disc 2. The playback control information isgenerated by the playback control information encoding unit 12responsive to an actuating input by a user and is recorded as theplayback control information file of the optical disc 2. By preparingthe new playback control information file in this manner, the videoprogram can be re-edited easily without decoding or encoding the videoand audio data.

[0149] The decoding device 10 of the optical disc recording/reproducingapparatus is explained in further detail.

[0150] Referring to FIG. 11, the decoding device 10 includes a mainbuffer 21 for temporarily storing multiplexed data sent from a buffer 6(FIG. 3), a first separation unit 22 for extracting a bitstream of theout-point side program from the main buffer 21 during skippingreproduction and a second separation unit 23 for extracting a bitstreamof the in-point side program from the main buffer 21 during skippingreproduction. The decoding device 10 also includes a first switchingunit 24 for time-divisionally switching between bitstreams of the AVprogram extracted by the first separation unit 22 for separation into avideo bitstream and an audio bitstream, and a second switching unit 25for time-divisionally switching between bitstreams of the AV programextracted by the second separation unit 23 for separation into a videobitstream and an audio bitstream.

[0151] The decoding device 10 also includes a first video buffer 26 forstorage of a video bitstream, separated by the first switching unit 24,a first audio buffer 27 for storage of an audio bitstream, separated bythe first switching unit 24, and a second audio buffer 29 for storage ofan audio bitstream, separated by the second switching unit 25. Thedecoding device 10 also includes a second audio buffer 29 for storing anaudio bitstream separated by the second switching unit 25, a first videodecoding unit 30 for extracting and decoding an audio bitstream storedin the first video buffer 26 and a first audio decoding unit 31 forextracting and decoding an audio bitstream stored in the first audiobuffer 27. The decoding device 10 also includes a second video decodingunit 32 for extracting and decoding a video bitstream stored in thesecond video buffer 28 and a second audio decoding unit 33 forextracting and decoding an audio bitstream stored in the second audiobuffer 29.

[0152] The decoding device 10 also includes a picture switchingoutputting unit 34 for switching between video data decoded by the firstvideo decoding unit 30 and by the second video decoding unit 32 foroutputting the selected decoded video data to an external equipment anda speech switching outputting unit 35 for switching between audio datadecoded by the first audio decoding unit 31 and by the second audiodecoding unit 33 for outputting the selected decoded video data to anexternal equipment. The decoding device 10 finally includes a displaycontroller 36 for controlling the picture switching outputting unit 34and the speech switching outputting unit 35 for controlling the outputtiming of the video and audio data and a timing controller 37 forgenerating system time clocks (STC) as reference synchronization signalsfor the device 10.

[0153] The main buffer 21 is fed with a bitstream of video data andaudio data multiplexed on the package basis from the buffer 6 (FIG. 3)at a bitrate Rin. This bitstream is data encoded for compression inaccordance with the MPEG 2 system. The main buffer 21 stores a bitstreamwhich is the multiplexed version of these video and audio data. Thisbitstream is transiently stored and subsequently extracted to the firstseparation unit 22 or the second separation unit 23 at a predeterminedtiming. The writing in the main buffer 21 is discontinued when it iswritten to its fall capacity.

[0154] During normal reproduction, other than skipping reproduction,video data and audio data of an AV program are stored in the main buffer21. During skipping reproduction, two AV programs, that is the out-pointside program and the in-point side program, are read out from theoptical disc 2 so as to be stored in the main buffer 21.

[0155] The first separation unit 22 and the second separation unit 23extract bitstreams of the multiplexed video and audio data from the mainbuffer 21 at a bitrate Rout. During the normal reproduction, one of thefirst separation unit 22 and the second separation unit 23 is operating,with the other being at a standstill. During skipping reproduction, thefirst separation unit 22 extracts only video data and audio data of theout-point side program of the two AV programs stored in the main buffer21, while the second separation unit 23 extracts only video data andaudio data of the in-point side program of the two AV programs stored inthe main buffer 21. The first separation unit 22 and the secondseparation unit 23 extract the video data and audio data during skippingreproduction based on the playback control information supplied from theplayback controller 8 (FIG. 3). This extraction is performed on thebasis of an index (P_last_index) of the past picture Plast of theplayback control information of the out-point side program and an index(P_in_index) of the in-point picture Pin of the playback controlinformation of the in-point side program. Of course, it is possible forthe first separation unit 22 to extract the in-point side program andfor the second separation unit 23 to extract the out-point side programto execute the subsequent operation, while it is also possible tointerchange AV programs processed by the respective separation units foreach skipping reproduction.

[0156] The first separation unit 22 sends the extracted out-point sideprogram to the first switching unit 24, while the second separation unit23 sends the extracted in-point side program to the second switchingunit 25. The first separation unit 22 and the second separation unit 23also extract system headers contained in the multiplexed data to sendthe extracted system header to the display controller 36.

[0157] The first switching unit 24 and the second switching unit 25separate multiplexed bitstream of vide and audio data into a bitstreamonly of video data and another bitstream only of audio data. Thebitstream of the out-point side program, separated by the firstswitching unit 24, is sent to the first video buffer 26. The audio bitstream of the out-point side program, separated by the first switchingunit 24, is sent to the first audio buffer 27. The bitstream of thein-point side program, separated by the second switching unit 25, issent to the second video buffer 28. The audio bit stream of theout-point side program, separated by the second switching unit 25, issent to the second audio buffer 29.

[0158] The first video buffer 26 and the second video buffer 28temporarily store the video bitstreams sent from the first switchingunit 24 and the second switching unit 25, respectively. The videobitstream, stored in the first video buffer 26, is extracted to thefirst video decoding unit 30 every predetermined data volume at a presettiming. The video bitstream, stored in the second video buffer 28, isextracted to the second video decoding unit 32 every predetermined datavolume at a preset timing.

[0159] The first audio buffer 27 and the second audio buffer 29temporarily store audio bitstreams sent from the first switching unit 24and the second switching unit 25, respectively. The audio bitstream,stored in the first audio buffer 27, is extracted to the first audiodecoding unit 31 at a predetermined timing every preset data volume. Theaudio bitstream, stored in the first audio buffer 29, is extracted tothe second audio decoding unit 33at a predetermined timing every presetdata volume.

[0160] The first video decoding unit 30 and the second video decodingunit 32 decode the video bitstream, encoded for compression inaccordance with the MPEG 2 system, to generate digital picture data. Thefirst video decoding unit 30 and the second video decoding unit 32decode the respective pictures in accordance with the decoding timestamp (DTS) for decoding affixed to each picture. Picture data decodedby the first video decoding unit 30 and the second video decoding unit32 are sent to the picture switching outputting unit 34.

[0161] The first audio decoding unit 31 and the second audio decodingunit 33 decode the audio bitstream, encoded for compression inaccordance with MPEG 2 system, to generate digital speech data. Thedigital speech data, decoded by the first and second audio decodingunits 31, 33, are sent to the speech switching outputting unit 35.

[0162] The picture switching outputting unit 34 selects one of thepicture data decoded by the first video decoding unit 30 or the picturedata decoded by the second video decoding unit 32, in order to outputthe selected picture data to an external equipment. This pictureswitching outputting unit 34 outputs each picture when the STC outputtedby the timing controller 37 coincides with the time managementinformation, that is presentation time stamp (PTS) of the playbackoutput, affixed to each picture. Also, the picture switching outputtingunit 34 sets its switch from the side of the first video decoding unit30 to the side of the second video decoding unit 32 during skippingreproduction at a display changeover timing between the out-pointpicture of the out-point side program and the in-point picture of thein-point side program . If the first video decoding unit 30 is decodingthe video bitstream of the in-point side program and the second videodecoding unit 32 is decoding the video bitstream of the out-point sideprogram, the picture switching outputting unit 34 of course sets itsswitch from the side of the second video decoding unit 32 to the side ofthe first video decoding unit 30.

[0163] The speech switching outputting unit 35 selects one of the speechdata decoded by the first audio decoding unit 31 and the speech datadecoded by the second audio decoding unit 33 to output the selectedspeech data to the external equipment. This speech switching outputtingunit 35 outputs speech data in synchronism with the picture dataoutputted by the picture switching outputting unit 34. During slippingreproduction, this speech switching outputting unit 35 sets its switchfrom the side of the first audio decoding unit 31 to the side of thesecond audio decoding unit 33 at a display switching timing between theout-point picture of the out-point side program and the in-point pictureof the in-point side program. Similarly to the picture switchingoutputting unit 34, the speech switching outputting unit 35 sets itsswitch from the side of the second audio decoding unit 33 to the side ofthe first audio decoding unit 31 if the first audio decoding unit 31 andthe second audio decoding unit 33 are decoding the audio bitstream ofthe in-point side program and the audio bitstream of the out-point sideprogram, respectively.

[0164] The display controller 36 controls the output timing of thepicture and speech data of the picture switching outputting unit 34 andthe speech switching outputting unit 35 based on the playback controlinformation sent from the playback controller 8 (FIG. 3) and from thetiming controller 37. The display controller 36 also controls theswitching of the picture switching outputting unit 34 and the speechswitching outputting unit 35 based on this playback control informationand the STC.

[0165] The timing controller 37generates the STC as the referencesynchronization signals of the decoding device 10. The timing controller37 sends this STC to the first video decoding unit 30, second videodecoding unit 32, first audio decoding unit 31 and to the second audiodecoding unit 33. Each decoding unit decodes the video and audio data ata timing derived from the STC. The timing controller 37 furnishes thisSTC to the display controller 36, which then controls the pictureswitching outputting unit 34 and the speech switching outputting unit 35at a timing derived from STC to output picture and audio data to changeover the switch state.

[0166] This timing controller 37 also switches the STC, based on PTS_Pinand PTS_Pout_end of the playback control information, at the time ofswitching from the out-point side program to the in-point side programduring skipping reproduction.

[0167] Specifically, this timing controller 37 switches the STC asfollows:

[0168] The timing controller 37 can be realized by a hardware structurecomprised of an STC generator 37 a, generating the STC, a subtractor 37b for subtracting a preset offset (STC_offset) from the STC generated bythe STC generator 37 a and a switch 37 c, as shown in FIG. 11. To aterminal A and a terminal B of the switch 37 c, the STC generated by theSTC generator 37 a is directly entered and the STC from which issubtracted an offset value by the subtractor 37 b, are entered,respectively. The input STC is outputted on switching between theseterminals A and B. The STC generator 37 a generates the STC set on asystem clock reference (SCR) of the out-point side program. The SCR isthe system time reference value or standard value. At this time, theswitch 37 c has been set to the side of the terminal A and directlyoutputs the STC as set on the SCR of the out-point side program. Whennext the STC is PTS_Pout_end of the out-point side program, the switch37 c is set to the side of the terminal B to output the STC less apreset offset value (STC_offset). This offset value (STC_offset) is thePTS_Pout_end of the playback control information of the out-point sideprogram less PTS_Pin of the playback control information of the in-pointside program. The STC generated at the same time as the switch 37 c isswitched to its terminal B is reset to an output value of the subtractor37 b. When the output value of the STC generator 37 a is reset, theswitch 37 c is set to the side of the terminal A to output an STC resetto the value of the SCR of the out-point side program.

[0169] By switching the STC as described above at the time of skippingreproduction, it is possible for the timing controller 37 to realize theseamless skipping reproduction.

[0170] The bitrate of the bitstream supplied to the main buffer 21 andthe bitrate of the bitstream read out from the main buffer 21 areassumed to be Rin and Rout, respectively. The bitrate of the videobitstream sent out from the first separation unit 22, the bitrate of thesystem header sent out from the first separation unit 22 and the bitrateof the system header sent out from the first separation unit 22 areassumed to be Rv1, Ra1 and Rsys1, respectively. Also, the bitrate of thebitstream sent from the second separation unit 23,the bitrate of theaudio bitstream sent from the second separation unit 23 and the bitrateof the system header sent form the second separation unit 23 are assumedto be Rv2, Ra2 and Rsys2, respectively. The sum of Rv1, Ra1 and Rsys1and the sum of Rv2, Ra2 and Rsys2 are assumed to be a first programbitrate Rpg1 and a second program bitrate Rpg2, respectively. Themaximum value of Rpg1 and Rpg2 is assumed to be the maximum programbitrate Rpg_max.

[0171] If the respective bitrates are defined as described above, thebitrate Rin of the bitstream sent to the main buffer 21 and the maximumprogram bitrate Rpg_max are related to each other by the followingequation:

Rin=Rpg_max+α(A>0)  (1)

[0172] The processing during skipping reproduction of the decodingdevice 10 is explained with reference to the flowchart shown in FIGS. 12to 14.

[0173] On starting the skipping reproduction, the timing controller 37sets the system time clock (STC) to the system time reference (STR) ofthe out-point side program at step SP1 in FIG. 12.

[0174] At the next step SP₂, the first video decoding unit 30 reads outa picture of the out-point side program from the first video buffer 26to decode each picture of the out-point side program in accordance withthe decoding time stamp (DTS). The display controller 36 controls thepicture switching outputting unit 34 to display the decoded pictures inaccordance with the presentation time stamp (PTS) of the pictures inquestion.

[0175] At the next step SP3, it is checked whether or not the in-pointside program has been stored in the second video buffer 28. If thenegative result is obtained at this step SP3, that is if the in-pointside program is not stored in the second video buffer 28, processingreverts to step ST2 to repeat the processing of steps SP2 and SP3. If anaffirmative result is obtained at this step SP3, that is if the in-pointside program has been stored in the second video buffer 28, processingtransfers to step SP4.

[0176] At this step SP4, the first video decoding unit 30 reads out thepictures of the out-point side program from the first video buffer 26 todecode the pictures of the out-point side program in accordance with thedecoding time stamp (DTS). The display controller 36 controls thepicture switching outputting unit 34 to display the decoded picture inaccordance with the presentation time stamp (PTS) of the picture inquestion. Simultaneously, the second video decoding unit 32 reads outthe picture of the in-point side program from the second video buffer 28to decode the pictures of the in-point side program in negligence of theDTS.

[0177] At the next step SP5, it is checked whether or not the decodingof the in-point picture of the in-point side program by the second videodecoding unit 32 has come to a close. If the negative result is obtainedat step SP5, that is if the decoding of the in-point picture by thesecond video decoding unit 32 has not come to a close, processingtransfers to step SP6. If the affirmative result is obtained at stepSP5, that is if the decoding of the in-point picture by the second videodecoding unit 32 has come to a close, processing transfers to step SP10shown in FIG. 13.

[0178] At step SP6, the value of STC and PTS_Pout_end shown in theplayback control information of the out-point side program are comparedto each other to check whether or not the display of the out-pointpicture of the out-point side program has come to a close. If, at thisstep SP6, STC is not coincident with PTS_Pout_end to give a negativeresult, that is if display of the out-point picture has not come to aclose, processing reverts to step SP4 to repeat the processing of stepsSP4 to SP6. If the affirmative result is obtained at this step SP6, thatis if display of the out-point picture has come to a close, processingtransfers to step SP20 shown in FIG. 14.

[0179] The fact that the affirmative result has been obtained at thisstep SP5 means that decoding of the in-point picture of the in-pointside program has come to a close before display of the pictures of theout-point side program has come to a close in its entirety, that is thatseamnless skipping reproduction is possible from the out-point sideprogram to the in-point side program.

[0180] Conversely, the fact that the affirmative result has beenobtained at the above step SP5 is that display of the out-point pictureof the out-point side program has come to a close before completion ofthe decoding of the in-point picture of the in-point side program comesto a close, that is that decoding of the in-point picture Pin has notcome to a close even although the display of the out-point picture Pouthas already come to a close, that is that seamless skipping reproductioncannot be made from the out-point side program to the in-point sideprogram.

[0181] The processing during skipping reproduction by the decodingdevice 10 is hereinafter separately explained for a case in whichskipping reproduction is possible and for a case in which skippingreproduction is not possible.

[0182] First, the processing for the case in which skipping reproductionis possible is explained.

[0183] At step SP10 shown in FIG. 13, it is checked whether the picturetype of the in-point picture is an I-picture or a P-picture, based onP_in_type shown in the playback control information. If the result ofcheck at this step SP10 is negative, that is if the in-point picture isa B-picture, processing transfers to step SP12. If the result of checkat this step SP10 is affirmative, that is if the in-point picture is anI- or P-picture, processing transfers to step SP11.

[0184] At step SP11, the second video decoding unit 32 reads out anddiscards the B-pictures stored in the second video buffer 28 from thein-point picture up to the next I- or P-picture. Then, processingtransfers from step SP1 to step SP12.

[0185] At step SP12, the value of STC is compared to PTS_Pout_endindicated in the playback control information of the out-point sideprogram in order to check whether or not the display of the out-pointpicture of the out-point side program has come to a close. If STC is notcoincident at this step SP12 such that a negative result is produced,that is if the display of the out-point picture has not come to a close,processing transfers to step SP13. If STC is coincident at this stepSP12 such that an affirmative result is produced, that is if the displayof the out-point picture has come to a close, processing transfers tostep SP14.

[0186] At step SP13, the first video decoding unit 30 reads out thepicture of the out-point side program from the first video buffer 26 todecode the pictures of the out-point side program in accordance with thedecoding time stamp (DTS). The display controller 36 controls thepicture switching outputting unit 34 to display the decoded picture inaccordance with the presentation time stamp (PTS) of the picture inquestion. The operation of the second video decoding unit 32 decodingthe in-point side program is halted. The processing reverts from thisstep SP13 to step SP12 to repeat the processing.

[0187] At step SP14, the timing controller 37 resets the value of theSTC displaying the in-point picture to a value of PTS_in of the in-pointside program simultaneously with the end of display of the out-pointpicture, that is when the STC is PTS_Pout_end.

[0188] At the next step SP15, the second video decoding unit 32 readsout the picture of the in-point side program from the second videobuffer 28 to decode the picture in accordance with the decoding timestamp (DTS) of each picture. The display controller 36 controls thepicture switching outputting unit 34 to display the decoded picture inaccordance with the presentation time stamp (PTS) of the picture inquestion.

[0189] By the above processing, the decoding device 10 can performskipping reproduction from the out-point side program to the in-pointside program.

[0190] The processing in case skipping reproduction in skippingreproduction is not possible is hereinafter explained.

[0191] At step SP20 shown in FIG. 14, the out-point picture isre-displayed.

[0192] At the next step SP21, it is checked whether or not decoding ofthe in-point picture has come to a close. If a negative result isobtained at this step SP21, that is if the decoding of the in-pointpicture has not come to a close, processing reverts to step SP20 tore-display the out-point picture Pout. If an affirmative result isobtained at this step SP21, that is if the decoding of the in-pointpicture has come to a close, processing reverts to step SP22. That is,the decoding device 10 causes the out-point picture to be repeatedlydisplayed until completion of decoding of the in-point picture tomaintain continuity of the playback picture under a state in whichskipping reproduction is not possible.

[0193] At step SP22, it is checked whether or not the picture type ofthe in-point picture is an I- or P-picture based on P_in_type shown inthe playback control information. If a negative result is obtained atthis step SP22, that is if the in-point picture is the B-picture,processing transfers to step SP24. If an affirmative result is obtainedat this step SP22, that is if the in-point picture is the I- orP-picture, processing transfers to step SP23.

[0194] At step SP23, the second video decoding unit 32 reads anddiscards the B-picture stored in the second video buffer 28 from thein-point picture up to the next I- or P-picture. Then, processingtransfers from step SP23 to step SP24.

[0195] At step SP24, the timing controller 37 resets the value of theSTC representing the in-point picture to a value of the PTS_in of thein-point side program.

[0196] At the next step SP25, the second video decoding unit 32 readsout pictures of the in-point side program from the second video buffer28 to decode the pictures of the in-point side program in accordancewith the decoding time stamp (DTS). The display controller 36 controlsthe picture switching outputting unit 34 to display the decoded picturein accordance with the presentation time stamp (PTS) for the picture inquestion.

[0197] By the above processing, the decoding device 10 can performskipping reproduction from the out-point side program to the in-pointside program.

[0198] Thus, the decoding device 10 can decide, during skippingreproduction, whether or not seamless reproduction can be upheld and, ifskipping reproduction can be upheld, the decoding device 10 can switchSTC to display the picture without any extraneous feeling. If skippingreproduction is not possible, it is possible to prohibit interruption indisplay.

[0199] The decoding and display timing in the decoding device 10 ishereinafter explained taking an instance in which the out-point sideprogram is reproduced up to B₀₇ as shown in FIG. 15A and reproduction isthen skipped to reproduce the in-point side program as from its B_(n5).

[0200] The first video decoding unit 30 sequentially decodes theout-point side program as from time point t⁻⁹ to terminate decoding ofB₀₇ (last picture Plast) at time point t⁻¹ to complete the decoding ofthe out-point side program, as shown in FIG. 15B. The second videodecoding unit 32 sequentially decodes the in-point side program as fromtime point t⁻⁶ to complete decoding up to B_(n4) at time point t₀, asshown in FIG. 15D. As for the pictures from I_(n2) to B_(n4), only I-and P-pictures are decoded, it being unnecessary to decode theB-picture. The reason is that pictures from I_(n2) to B₄ are notdisplayed, while only I- and P-pictures during this interval arerequired for decoding P_(n5) (in-point picture).

[0201] The decoding device 10 displays the decoded out-point sideprogram until time t₀ in its PTS. At a time point to when the display ofthe out-point picture Pout comes to a close, the STC is reset to thevalue of PTS_Pin, whilst the decoded in-point side program issequentially displayed in accordance with the PTS of the respectivepictures, as shown in FIG. 15E.

[0202] By this decoding and display, the decoding device 10 cancontinuously display the out-point picture and the in-point picture asshown in FIG. 15F to effect seamless reproduction of the out-point sideprogram and the in-point side program.

[0203] Referring to FIG. 16, transition in the bit occupying volumes ofthe main buffer 21, first video buffer 26 and the second video buffer 28is explained.

[0204]FIG. 16A shows the bit occupying volume of the multiplexed data inthe main buffer 21. The bit occupying volume ranges from MB_size as thecapacity of the main buffer 21 to 0. FIG. 16B shows the bit occupyingvolume of the video bitstream of the out-point side program in the firstvideo buffer 26. This bit occupying volume ranges from VB1_size as thecapacity of the first video buffer 26 to 0. Similarly, FIG. 16C showsthe bit occupying volume of the video bitstream of the in-point sideprogram in the second video buffer 28. This bit occupying volume rangesfrom VB2_size as the capacity of the second video buffer 28 to 0.

[0205] The term T1 shows the state of the first video decoding unit 30decoding the out-point side program. At this time, the output bitrate ofthe main buffer 21 is increased at a rate of Rin−Rpg1 until the mainbuffer 21 is charged to its capacity. For Rpg1=Rpg_max, the increasingrate is minimum. In such case, the increasing rate of the bit occupyingvolume is shown by the following equation (2):

Rin−Rpg_max=(Rpg_max+α)—Rpg_max=α  (2)

[0206] The term T2 is the state the main buffer 21 is charged to itscapacity and, similarly to the term T1, denotes the state the firstvideo decoding unit 30 is decoding the out-point side program. Theoutput bitrate of the main buffer 21 is Rpg1.

[0207] The term T3 is a state the first video decoding unit 30 isdecoding the out-point side program and the second video decoding unit32 is decoding the in-point side program. At this time, the outputbitrate from the main buffer 21 is Rpg1+Rpg2, with the bit occupyingvolume of the multiplexed data in the main buffer 21 decreasing at arate of Rpg1−Rpg2−Rin. The decreasing rate is maximum for Rpg1Rpg2=Rpg_max. The decreasing rate of the bit occupying volume at thistime is indicated by the equation (3): $\begin{matrix}{\begin{matrix}{{{Rpg1} + {Rpg2} - {Rin}} = {{2 \times {Rpg}\quad \_ \quad \max} - \left( {{{Rpg}\quad {\_ max}} + \alpha} \right)}} \\{= {{{Rpg}\quad \_ \quad \max} - \alpha}}\end{matrix}.} & (3)\end{matrix}$

[0208] Skipping reproduction is performed across the terms T3 and T4.

[0209] The term T4 denotes the state the second video decoding unit 32is decoding the in-point side program. At this time, the output bitratefrom the main buffer 21 is Rpg2, with the bit occupying volume ofmultiplexed data in the main buffer 21 increasing at a rate of Rin−Rpg2until the main buffer 21 is charged to its fill capacity. The increasingrate is minimum for Rpg=Rpg_max, in which case the bit increasing rateis indicated by the equation (4):

Rin−Rpg_max=(Rpg_max+α)−Rpg_max=α  (4).

[0210] The term T5 denotes the state the main buffer 21 is charged toits fall capacity and, similarly to the term T4, is the state the secondvideo decoding unit 32 is decoding the in-point side program. The outputbitrate from the main buffer 21 is Rpg2.

[0211] The transition of the bit occupying volume as indicated for termsT1 to T3 is repeated every skipping reproduction.

[0212] The time lengths of the terms T1 and T3 are explained.

[0213] The time length of the term T1 denotes the time which elapsessince start of supply of the in-point side program to the second videobuffer 28 until completion of decoding of the in-point picture Pin in astate in which the first video decoding unit 30 and the second videodecoding unit 32 are decoding the out-point side program and thein-point side program simultaneously. If the number of pictures to bedecoded from the leading picture Pfirst to the in-point picture Pin isNdec, the time length of the term T3 is given by the following equation(5): $\begin{matrix}{{T3} = {\sum\limits_{i = 0}^{Ndec}\left( {2 + {{{rff}\lbrack i\rbrack}/\left( {2 \times {frame\_ rate}} \right)} + {{decode\_ start}{\_ up}{{\_ delay}.}}} \right.}} & (5)\end{matrix}$

[0214] If GOP length is N and the interval of the P-pictures is M, themaximum value of the number of pictures Ndec to be decoded from theleading picture Pfirst to the in-point picture Pin is given by thefollowing equation (6):

Ndec=N+M−1  (6)

[0215] From the above equations (5) and (6), the maximum value T3_max ofthe term T3 is given by the following equation (7): $\begin{matrix}{\begin{matrix}{{{T3}\quad \_ \quad \max} = \quad {{\overset{N + {M\quad \_ 1}}{\sum\limits_{i = 0}}{\left( {2 + {{rff}\lbrack i\rbrack}} \right)/\left( {2 \times {frame\_ rate}} \right)}} +}} \\{\quad {{decode\_ start}{\_ up}{\_ delay}}}\end{matrix}.} & (7)\end{matrix}$

[0216] It is noted that decode_start_up_delay=1.75 mbit/Rpg_max. If thei'th picture is a B-picture, rff[i] is a value of repeat_first_field ofthe picture, whereas, if the i'th picture is an I- or P-picture, rff[i]is a value of repeat_first_field of the previous I- or P-picture.

[0217] During the T3 period, two programs, namely the out-point sideprogram and the in-point side program, are outputted from the mainbuffer 21 at a rate of 2*Rpg_max at the maximum. The main buffer 21 isrequired to have the capacity of supplying the two programs, namely theout-point side program and the in-point side program during the periodof T3_max without underflowing. That is, the capacity MB_size of themain buffer 21 is given by the following equation (8): $\begin{matrix}{\begin{matrix}{{{MB}\quad \_ \quad {size}} = {{T3}\quad \_ \quad \max \times \left( {{2 \times {Rpg}\quad {\_ max}} - {Rin}} \right)}} \\{= {{T3}\quad \_ \quad \max \times \left( {{{Rpg}\quad \_ \quad \max} - \alpha} \right)}}\end{matrix}.} & (8)\end{matrix}$

[0218] The time length of the term T1 is the time which elapses sincethe bit occupying volume of the main buffer 21 is 0 until it is MB_sizein the state the first video decoding unit 30 is decoding the out-pointside program. The term T1 is given by the following equation (9):$\begin{matrix}\begin{matrix}{{T1} = {{MB}\quad {{\_ size}/\left( \left( {{Rin} - {{Rpg}\quad {\_ max}}} \right) \right.}}} \\{= {{MB}\quad {{\_ size}/\alpha}}}\end{matrix} & (9)\end{matrix}$

[0219] If skipping reproduction is repeated on end, there is thenecessary minimum time since the in-point picture until the nextout-point picture, thus imposing limitation on the positions of thein-point picture and the out-point picture. The reason is that, forskipping reproduction, the main buffer 21 needs to be charged to itsfull capacity. That is, the necessary minimum time for skippingreproduction from the in-point picture to the out-point picture is givenby the following equation (10):

Lmin=T1  (10).

[0220] For skipping reproduction, the user specifies the out-pointpicture and the in-point picture in advance. The optical discrecording/reproducing apparatus 1 performs skipping reproduction inaccordance with the out-point picture and the in-point picture set inadvance. That is, the operating input unit 11 generates the controlinformation responsive to the out-point picture and the in-point picturespecified by the user. The playback controller 8 is responsive to thiscontrol information to control the various parts to execute skippingreproduction.

[0221] When the user specifies the out-point picture and the in-pointpicture, the playback controller 8 checks in advance whether or not, ifthe skipping reproduction is executed with the out-point picture and thein-point picture as specified by the user, seamless reproduction ispossible. The playback controller 8 then indicates the results ofdecision on the decision information display unit 17. The method fordiscriminating the possibility of seamless reproduction is hereinafterexplained.

[0222] If the bitrate of the out-point side program is Rpg_out(t) andthe bitrate of the in-point picture is Rpg_in(t), the bit occupyingvolume MB_bit in the main buffer 21 necessary for starting the decodingof the in-point side program is given by the equation (11):

MB_bit=T3×(Rpg_in(t)+Rpg_out(t)−Rin)  (11).

[0223] The bit storage time L, which is the time(domain T1 in FIG. 16A)necessary for the bit occupying volume in the main buffer 21 to bestored from 0 to MB_bit, in case only the out-point side program isbeing decoded, is given by the equation (12):

L=MB_bit/(Rin−Rpg_out(t))  (12).

[0224] If, in the out-point side program, shown in FIG. 4, the PTS ofthe out-point picture Pout is PTS_Pout, and PTS of the in-point pictureprevious_Pin is PTS_previous_Pin, the inter-skip time Lout_in, which isthe time difference between the out-point picture Pout and the previousin-point picture previous_Pin, is given by the equation (13):

Lout_in=(PTS_Pout−PTS_previous_Pin)×90 KHz  (13).

[0225] Foe seamless reproduction during skipping reproduction, theinter-skip time Lout_in needs to be longer than the bit storage time L.That is, the following equation (14):

Lout_in≧L  (14)

[0226] needs to be met.

[0227] Conversely, if the inter-skip time Lout_in is less than the bitstorage time L, the main buffer 21 is subjected to underflow during thedomain T3 shown in FIG. 16A. Therefore, the decoding of the in-pointpicture Pin cannot be completed until the display end time PTS_Pout_endof the out-point picture Pout, so that seamless reproduction is notpossible.

[0228] The controller 8 checks the possibility of seamless reproductionusing the above equation (14) to display the result of check on thedecision information display unit 17.

[0229] In the optical disc recording/reproducing apparatus according tothe first embodiment of the present invention, as described above, theout-point side program and the in-point side program are decoded inparallel by the two decoding units. The out-point picture, display ofwhich is terminated at PTS_Pout_end, and the in-point picture Pin,display of which is started at PTS_Pin, are continuously outputted,while the STC is reset from PTS_Pout_end to PTS_Pin at the changeovertiming from the out-point picture to the in-point picture. This enablesthe present optical disc recording/reproducing apparatus 1 to effectseamless skipping reproduction as continuity is upheld before and afterthe switching point.

[0230] It is also possible with the present optical discrecording/reproducing apparatus to check whether or not skippingreproduction is possible as seamless reproduction.

Second Embodiment

[0231] An optical disc recording/reproducing apparatus according to asecond embodiment of the present invention is hereinafter explained. Inthis second embodiment, only the structure of the decoding device hasbeen modified from that of the decoding device 10 of the above-describedfirst embodiment. That is, the present optical discrecording/reproducing apparatus is the same as the apparatus of thefirst embodiment except the structure of the decoding device 10.Therefore, only a decoding device associated with this decoding device10 is explained in detail. The component parts which are the same asthose of the decoding device 10 are depicted by the same referencenumerals and are not explained specifically.

[0232] The decoding device of the optical disc recording/reproducingapparatus of the second embodiment of the present invention is explainedin detail.

[0233]FIG. 17 shows the block diagram of the decoding device used in thepresent optical disc recording/reproducing apparatus of the secondembodiment. A decoding device 40, shown in FIG. 17, is used in place ofthe decoding device 10 of the optical disc recording/reproducing of thefirst embodiment shown in FIG. 3.

[0234] The decoding device 40 includes a main buffer 21 for transientstorage of multiplexed data composed of video data and audio datasupplied from the buffer 6 (FIG. 3), a separation unit 41 for extractinga bitstream stored in the main buffer 21 to separate the bitstream intoa bitstream of the out-point side program and a bitstream of thein-point side program during skipping reproduction, and a switching unit42 for time-divisionally switching between the bitstreams of the AVprogram extracted by the separation unit 41 for separation into thevideo bitstream and the audio bitstream.

[0235] The decoding device 40 also includes a first video buffer 43 forstoring the video bitstream of the out-point side program duringskipping reproduction, and a second video buffer 44 for storing thevideo bitstream of the in-point side program during skippingreproduction. The decoding device 40 also includes a first audio buffer45 for storage of the audio bitstream of the out-point side programduring skipping reproduction and a second audio buffer 46 for storage ofthe audio bitstream of the in-point side program during skippingreproduction. The decoding device 40 also includes a picture switchingunit 47 for switching between the video bitstream stored in the firstvideo buffer 43 and the video bitstream stored in the second videobuffer 44, and a speech switching unit 48 for switching between theaudio bitstream stored in the first audio buffer 45 and the audiobitstream stored in the second audio buffer 46.

[0236] The decoding device 40 also includes a video decoding unit 49switched by the picture switching unit 47 for decoding the input videobitstream, and an audio decoding unit 50 switched by the speechswitching unit 48 for decoding an input audio bitstream. The decodingdevice 40 finally includes a display controller 51 for controlling theoutput timing of the video and audio data and a time controller 37 forgenerating system time clocks (STC) as the reference synchronizationsignal of the device.

[0237] The main buffer 21 is fed with bitstreams of the video data andaudio data multiplexed on the package basis from the buffer 6 (FIG. 3)at a bitrate Rin. This bitstream is transiently stored in the mainbuffer 21 so as to be then extracted to the separation unit 41 at apreset timing. The writing in the main buffer 21 is halted when it ischarged to its full capacity.

[0238] During normal reproduction, there are stored in this main buffer21 the video data and the audio data of a sole AV program. Duringskipping reproduction, the two AV programs, namely the out-point sideprogram and the in-point side program, are read out from the opticaldisc 2 so as to be stored in the main buffer 21.

[0239] The separation unit 41 extracts the bitstreams of the multiplexedvideo and audio data at a bitrate Rout from the main buffer 21. Theseparation unit 41 extracts data of the out-point side program and dataof the in-point side program, during skipping reproduction, as itseparates the two data. At this time, the separation unit 41 extractsvideo and audio data at the time of skipping reproduction based on theplayback control information supplied from the playback controller 8(FIG. 3). For example, the video and audio data are extracted based onthe index P_last_index of the last picture Plast of the playback controlinformation of the out-point side program and the index P-in-index ofthe in-point picture Pin of the playback control information of thein-point side program. The separation unit 41 sends the extracted datato the switching unit 42. The separation unit 41 also extracts thesystem header contained in the multiplexed data of the in-point sideprogram and the out-point side program to send the system header to thedisplay controller 51.

[0240] The switching unit 42 time-divisionally separates bitstreams ofthe video and audio data multiplexed in each of the out-point sideprogram and the in-point side program to provide a bitstream only ofvideo data and a bitstream only of the audio data. The video bitstreamof the out-point side program, separated by the switching unit 42, issent to the first video buffer 43. The video bitstream of the in-pointside program, separated by the switching unit 42, is sent to the secondvideo buffer 44. The audio bitstream of the out-point side program,separated by the switching unit 42, is sent to the first audio buffer45. The audio bitstream of the in-point side program, separated by theswitching unit 42, is sent to the second audio buffer 46.

[0241] The first video buffer 43 and the second video buffer 44temporarily store the video bitstreams supplied from the switching unit42. The picture switching unit 47 switches between the video bitstreamstored in the first video buffer 43 and the video bitstream stored inthe second video buffer 44 to extract the selected video bitstream tothe video decoding unit 49 at predetermined timing on the predetermineddata volume basis.

[0242] The first audio buffer 45 and the second audio buffer 46temporarily store the audio bitstream sent from the switching unit 42.The speech switching unit 48 switches between the audio bitstream storedin the first audio buffer 45 and the audio bitstream stored in thesecond audio buffer 46 to extract the selected audio bitstream to theaudio decoding unit 50 at a timing synchronized with the video decodingtiming.

[0243] The video decoding unit 49 decodes the video bitstream encodedfor compression by the MPEG 2 system to generate digital picture data.This video decoding unit 49 is adapted to decode each picture at a speedhigher than the video display speed. For example, the video decodingunit 49 has a decoding speed twice the minimum decoding speed necessaryfor real-time display of video data supplied in real-time. During normalreproduction, the video decoding unit 49 decodes each picture at anormal decoding speed in accordance with the time management information(decoding time stamp DTS) for decoding affixed to each picture. On theother hand, this video decoding unit 49 switches between the video dataof the out-point side program stored in the first video buffer 43 andvideo data of the in-point side program stored in the second videobuffer 44 during skipping reproduction to read out the so-selected videodata. The video decoding unit 49 alternately decodes during skippingreproduction the out-point side program and the in-point side program onthe predetermined data volume basis at a decoding speed twice the usualdecoding speed in negligence of the DTS. The data volumes at which toswitch between the out-point side program and the in-point side programmay be of any suitable value. The video decoding unit 49 switchesbetween the out-point side program and the in-point side program on thepicture or macro-block basis. The digital picture data, decoded by thisvideo decoding unit 49, is sent to outside under control by the displaycontroller 51.

[0244]FIG. 18 shows a block diagram of the video decoding unit 49.

[0245] The video decoding unit 49 includes a variable length decodingcircuit 52 for variable-length decoding an input video bitstream, aninverse DCT (inverse discrete cosine transform) circuit 53 for IDCTingthe variable length decoded video bitstream and a dequantization circuit54 for dequantizing the IDCTed video bitstream. The video decoding unit49 also includes an addition circuit 55 for adding an output picture ofthe dequantization circuit 54 and a motion-compensated reference pictureto each other, a first frame memory 56 for transiently storing an outputpicture, a second frame memory 57 for transiently storing an outputpicture and a motion-compensation circuit 58 for motion-compensatingpictures stored in the first and second frame memories 56, 57 forgenerating a reference picture.

[0246] The variable length decoding circuit 52, IDCT circuit 53,dequantization circuit 54 and the motion-compensation circuit 58 canperform processing at a speed twice the usual processing speed. Each ofthe first and second frame memories 56, 57 includes a frame memory forforward prediction and a frame memory for backward prediction. The firstframe memory 56 stores each picture of the out-point side program, forexample, during skipping reproduction. The second frame memory 57 storeseach picture of the out-point side program, for example, during skippingreproduction. During operation, the variable length decoding circuit 52,IDCT circuit 53, dequantization circuit 54 and the motion-compensationcircuit 58 time-divisionally switch between the out-point side programand the in-point side program. Depending on the timing, themotion-compensation circuit 58 switches between the first frame memory56 and the second frame memory 57 for picture extraction and motioncompensation.

[0247] The audio decoding unit 50 decodes an audio bitstream encoded forcompression in accordance with MPEG 2 system to generate digital speechdata. The digital speech data, decoded by the audio decoding unit 50, issent to outside under control by the display controller 51.

[0248] The display controller 51 controls the output timing of picturedata and audio data of the video decoding unit 49 and the audio decodingunit 50 based n the playback control information sent from the playbackcontroller 8 and the STC sent from the timing controller 37.

[0249] Specifically, the display controller 51 outputs each picturedecoded by the video decoding unit 49 when the STC generated by thetiming controller 37 coincides with the time management information(presentation time stamp PTS) of the playback output affixed to eachpicture. During skipping reproduction, the display controller 51switches the output picture from the out-point side program to thein-point side program at a display switching timing between theout-point picture of the out-point side program and the in-point pictureof the in-point side program.

[0250] The display controller 51 also outputs speech data in synchronismwith picture data outputted by the video decoding unit 49. Duringskipping reproduction, the display controller 51 switches output audiodata from the out-point side program to the in-point side program at adisplay switching timing between an out-point picture of the out-pointside program and the in-point picture of the in-point side program.

[0251] The bitrate of the bitstream supplied to the main buffer 21 andthat of the bitstream read out from the main buffer 21are assumed to beRin and Rout, respectively. The bitrate of the video bitstream sent tothe first video buffer 43 and that of the video bitstream sent to thesecond video buffer 44 are assumed to be Rv1 and Rv2, respectively. Thebitrate of the audio bitstream sent to the first audio buffer 45 andthat of the audio bitstream sent to the second audio buffer 46 areassumed to be Ra1 and Ra2, respectively. The bitrates of the systemheader sent from the separation unit 41 are assumed to be Rsys1 andRsys2. The sum of Rv1, Ra1 and Rsys1 and the sum of Rv2, Ra2 and Rsys2are assumed to be a first program bit rate Rpg1 and a second program bitrate Rpg2, respectively. The maximum value of Rpg1 and Rpg2 is assumedto be the maximum program bitrate Rpg_max.

[0252] If the respective bitrates are defined as above, the followingrelation:

Rin=Rpg_max+α(A>0) Rout≦×Rpg_max  (15)

[0253] holds between the bitrate Rin of the bitstream sent to the mainbuffer 21 and the maximum program bitrate Rpg_max.

[0254] The processing executed by the decoding device 40 during skippingreproduction is hereinafter explained with reference to a flowchartshown in FIGS. 19 to 21.

[0255] If skipping reproduction is started, the timing controller 37sets the system time clock STC to the system clock reference (SCR) ofthe out-point side program at step SP31 in FIG. 19.

[0256] At the next step SP32, the video decoding unit 49 reads outpictures of the out-point side program from the first video buffer 43 todecode the pictures of the out-point side program in accordance with thedecoding time stamp (DTS). The display controller 51 controls the videodecoding unit 49 to display the decoded pictures in accordance with thepresentation time stamp PTS of the pictures in question. At this time,the video decoding unit 49 performs the decoding at a speed equal to thepicture display speed.

[0257] At the next step SP33, it is checked whether or not the in-pointside program has been stored in the second video buffer 44. If theresult of check of this step SP33 is negative, that is if the in-pointside program has not been stored in the second video buffer 44,processing transfers to step SP32 to repeat the processing of the stepsSP32 to SP33. If the result of check of this step SP33 is affirmative,that is if the in-point side program has been stored in the second videobuffer 44, processing transfers to step SP34.

[0258] At step SP34, the video decoding unit 49 reads out pictures ofthe out-point side program from the first video buffer 43, while readingout pictures of the in-point side program from the second video buffer44, in order to decode the pictures of the out-point side program andthe in-point side program in negligence of the decoding time stamp(DTS). At this time, the video decoding unit 49 performs decoding at adouble speed, that is at a speed twice the picture display speed, whilealternately decoding the out-point side program and the in-point sideprogram on the predetermined data volume basis. The data decoding volumebasis for alternate decoding may be arbitrary, such that decoding may bemade on switching between the out-point side program and the in-pointside program on the macro-block basis or on the picture basis. Thedisplay controller 51 controls the video decoding unit 49 to display thedecoded out-point side program in accordance with the presentation timestamp PTS of the pictures in question.

[0259] At the next step SP35, it is checked whether or not decoding ofthe of the in-point picture of the in-point side program has come to aclose. If the result of check of step SP35 is negative, that is ifdecoding of the in-point picture by the video decoding unit 49 has notcome to a close, processing transfers to step SP36. If the result ofcheck of step SP35 is affirmative, that is if decoding of the in-pointpicture by the video decoding unit 49 has come to a close, processingtransfers to step SP40.

[0260] At step SP36, the value of STC is compared to PTS_Pout_endindicated in the out-point side program to check whether or not displayof the out-point pictures of the out-point side program has come to aclose. If STC is not coincident with PTS_Pout_end, such that the resultof check of step SP36 is negative, that is if display of the out-pointpictures has not come to a close, processing reverts to step SP34 torepeat the processing of steps SP34 to 36. If the result of check ofstep SP36 is affirmative, that is if the display of the out-point sideprogram has come to a close, processing transfers to step SP50 shown inFIG. 21.

[0261] The fact that an affirmative result has been obtained at stepSP35 means that decoding of the in-point picture of the in-point sideprogram has come to a close before display of the pictures of theout-point side program has come to a close in its entirety, that is thatseamless skipping reproduction from the out-point side program to thein-point side program is possible.

[0262] Conversely, the fact that an affirmative result has been obtainedat step SP36 means that decoding of the out-point pictures of theout-point side program has come to a close before completion of thein-point picture of the in-point side program, that is that decoding ofthe in-point picture Pin has not come to a close even although thedisplay of the out-point pictures Pout has come to a close, in otherwords, that seamless skipping reproduction from the out-point sideprogram to the in-point side program is not possible.

[0263] The processing during skipping reproduction of the decodingdevice 40 is hereinafter explained separately for a case in whichskipping reproduction is possible and for a case in which skippingreproduction is not possible.

[0264] First, the processing in which skipping reproduction is possibleis explained.

[0265] At step S40 in FIG. 20, it is checked whether or not the pictureof an in-point picture is an I-picture or a P-picture. This check can bemade on the basis of P_in_type indicated in the playback controlinformation. If the result of check at this step SP40 is negative, thatis, if the in-point picture is a B-picture, processing transfers to stepSP42. If the result of check at this step SP40 is affirmative, that is,if the in-point picture is an I-picture or a P-picture, processingtransfers to step SP41.

[0266] At step SP41, the video decoding unit 32 reads out and discardsB-pictures from the in-point picture to the next I- or P-picture storedin the second video buffer 44. After this step SP41, processingtransfers to step SP42.

[0267] At step SP42, the value of the STC is compared to PTS_Pout_endindicated in the playback control information of the out-point sideprogram to check whether or not display of the out-point pictures of theout-point side program has come to a close. If, at this step SP42, STCis not coincident with PTS_Pout_end, such that a negative result isobtained, that is if the display of the out-point pictures has not cometo a close, processing transfers to step SP43. If, at this step SP42,STC is coincident with PTS_Pout_end, such that an affirmative result isobtained, that is if the display of the out-point pictures has come to aclose, processing transfers to step SP44.

[0268] At step SP43, the video decoding unit 49 reads out pictures ofthe out-point side program from the first video buffer 43 to decode thepictures of the out-point side program in accordance with the decodingtime stamp DTS. Simultaneously, the display controller 51 controls thevideo decoding unit 49 to display the decoded pictures in accordancewith the presentation time stamp PTS of the pictures in question. Afterthis step SP43, processing reverts to step SP42 to repeat theprocessing.

[0269] At step SP44, at the same time as display of the out-pointpictures is terminated, that is when the STC is equal to PTS_Pout_end,the timing controller 37 resets the value of the STC displaying thein-point picture to a value of PTS_in of the in-point side program.

[0270] At the next step SP45, the video decoding unit 49 reads outpictures of the in-point side program from the second video buffer 44 todecode the pictures in accordance with the decoding time stamp DTS ofeach picture. The display controller 51 controls the video decoding unit49 to display the decoded pictures in accordance with the presentationtime stamp PTS of the pictures in question. The decoding operation atthis time is executed at the normal decoding speed.

[0271] By the above processing, the decoding device 40 can performskipping reproduction from the out-point side program to the in-pointside program.

[0272] The processing in case seamless reproduction in skippingreproduction is not possible is now explained.

[0273] At step SP50, shown in FIG. 21, an out-point picture isre-displayed.

[0274] At the next step SP51, it is checked whether or not decoding ofthe in-point picture has come to a close. If the result of check of thisstep SP51 is negative, that is if the decoding of the in-point picturehas not come to a close, processing reverts to step SP50 to re-displaythe out-point picture Pout. If the result of check of this step SP51 isaffirmative, that is if the decoding of the in-point picture has come toa close, processing reverts to step SP52. Thus, the decoding device 40repeatedly displays the out-point picture until end of decoding of thein-point picture to uphold the continuity of the reproduced picture incase seamless reproduction is not possible.

[0275] At step SP52, it is checked whether or not the picture type ofthe in-point picture is an I-picture or a P-picture. This check can bemade based on P_in_type indicated in the playback control information.If the result of check at this step SP52 is negative, that is if thein-point picture is a B-picture, processing transfers to step SP54. Ifthe result of check at this step SP52 is affirmative, that is if thein-point picture is an I-picture or a P-picture, processing transfers tostep SP53.

[0276] At step SP53, the video decoding unit 49 reads and discardsB-pictures from the in-point picture to the next I- or P-picture storedin the second video buffer 44. After this step SP53, processingtransfers to step SP54.

[0277] At step SP54, the timing controller 37 resets the value of theSTC displaying the in-point picture to a value of PTS_in of the in-pointside program.

[0278] At the next step SP55, the video decoding unit 49 reads out anddiscards a pictures of the in-point side program from the second videobuffer 44 to decode the pictures of the in-point side program inaccordance with the decoding time stamp DTS. The display controller 51controls the video decoding unit 49 to display the decoded pictures inaccordance with the presentation time stamp PTS of the pictures inquestion.

[0279] By the above processing, the decoding device 40 can performskipping reproduction from the out-point side program to the in-pointside program.

[0280] Thus, the decoding device 40 judges whether or not seamlessreproduction can be upheld during skipping reproduction. If seamlessreproduction is possible, the STC can be switched to display thepictures without producing extraneous feeling, whereas, even if seamlessreproduction is not possible, there is no fear of display interruption.

[0281] The timing of decoding and display in the decoding device 40 isnow explained taking an example of reproducing the pictures of theout-point side program, up to B₀₇, then skipping the reproduction andreproducing the pictures of the out-point side program from P_(n5), asshown in FIG. 22A.

[0282] The video decoding unit 49 sequentially decodes the pictures ofthe out-point side program as from time point t⁻⁹, as shown in FIG. 22B.When B₀₇ (last picture Plast) has been decoded at time t⁻¹, decoding ofthe out-point side program is terminated. The video decoding unit 49then sequentially decodes the in-point side program from time point t₆,as shown in FIG. 22D, to complete the decoding up to B_(n4) at time t₀.It is noted that the video decoding unit 49 operates at a double speedduring the time of decoding both the out-point side program and thein-point side program simultaneously, that is since time point t⁻⁶ untiltime point t⁻⁰, by way of reproducing the out-point side program and thein-point side program alternately every preset data volume. It is notedhowever that only I- and P-pictures need to be decoded during the timefrom I_(n2) until B₄ of the in-point side program, while there is nonecessity of decoding the B-pictures. The reason is that no pictures aredisplayed from I_(n2) up to B₄, while only the I- and P-pictures duringthis time interval are needed for decoding the in-point picture P₅.

[0283] The v49 displays the decoded out-point side program until timepoint to in accordance with its PTS, as shown in FIG. 22C. At the timepoint to when the display of the out-point picture Pout comes to aclose, the STC is reset to the value of PTS_Pin, while the decodedin-point side program is sequentially displayed in accordance with thePTS of each picture, as shown in FIG. 22E.

[0284] By this decoding and display, the decoding device 40 cancontinuously display the out-point picture and the in-point picture insuccession, as shown in FIG. 22F, to seamlessly reproduce the out-pointside program and the in-point side program.

[0285] The transition of the bit occupying volumes of the main buffer21, first video buffer 43 and the second video buffer 44 during skippingreproduction is explained with reference to FIG. 23.

[0286]FIG. 23A shows the bit occupying volume of multiplexed data in themain buffer 21. This bit occupying volume is varied from MB_size as thecapacity of the main buffer 21 to 0. FIG. 23B shows the bit occupyingvolume of the video bitstream of the out-point side program in the firstvideo buffer 43. This bit occupying volume is varied from VB1_size asthe capacity of the first video buffer 43 to 0. Similarly, FIG. 23Cshows the bit occupying volume of the video bitstream of the in-pointside program in the second video buffer 44. This bit occupying volume isvaried from VB2_size as the capacity of the second video buffer 44 to 0.

[0287] The term T1 indicates a state in which the video decoding unit 49is decoding the out-point side program at the normal decoding speed. Atthis time, the output bitrate of the main buffer 21 is Rpg1, with thebit occupying volume of the multiplexed data in the main buffer 21increasing at a rate of Rin−Rpg1 until the main buffer 21 is charged toits full capacity. The increasing rate of the bit occupying volume isminimum for Rpg1=Rpg_max and is represented by the equation (16):

Rin−Rpg_max=(Rpg_max+α)−Rpg_max=α  (16).

[0288] The term T2 denotes the state in which the main buffer 21 hasbeen charged to its capacity and, similarly to the term T1, denotes thestate in which the video decoding unit 49 is decoding the out-point sideprogram at the normal decoding speed. The output bitrate from the mainbuffer 21 is Rpg1.

[0289] The term T3 denotes a state in which the video decoding unit 49is decoding the out-point side program and the in-point side program ata double speed. At this time, the output bitrate from the main buffer 21is Rpg1+Rpg2, with the bit occupying volume of the multiplexed data inthe main buffer 21 decreasing at a rate of Rpg1+Rpg_max. The bitoccupying volume decreasing rate is maximum for Rpg1=Rpg2=Rpg_max. Thebit occupying volume decreasing rate in this case is given by theequation (17):

Rpg1+Rpg2−Rin=2×Rpg_max−(Rpg_max+α)=Rpg_max−α  (17)

[0290] Skipping occurs since the term T3 until the term T4.

[0291] The term T4 denotes the state in which the video decoding unit 49is decoding the in-point side program at the normal decoding speed. Atthis time, the output bitrate of the main buffer 21 is Rpg2, with themultiplexed data bit occupying volume in the main buffer 21 increasingat a rate of Rin−Rpg2 until the main buffer 21 is charged to its fullcapacity. The increasing rate is minimum for Rpg2=Rpg_max, in which casethe increasing rate of the bit occupying volume is given by the equation(18):

Rin−Rpg_max=(Rpg_max+α)−Rpg_max=α  (18).

[0292] The term T5 denotes a state in which the main buffer 21 has beencharged to its full capacity and, similarly to the term T4, denotes thestate n which the video decoding unit 49 is decoding the in-point sideprogram at a normal decoding speed. The output bitrate from the mainbuffer 21 is Rpg2.

[0293] The transition of the bit occupying volume during the terms T1 toT3 is repeated every skipping reproduction.

[0294] The time length of the terms T I and T3 is explained.

[0295] The time length of the term T3 denotes the time which elapsessince start of supply of the out-point side program to the second videobuffer 44 until end of decoding of the in-point picture Pin in a statein which the video decoding unit 49 is decoding the out-point sideprogram and the in-point side program simultaneously. If the number ofpictures decoded as from the leading picture Pfirst up to the in-pointpicture Pin is Ndec, the time length of the term T3 is given by theequation (19): $\begin{matrix}{{T3} = \quad {{\sum\limits_{i = 0}^{N + {M\quad \_ 1}}{\left( {2 + {{rff}\lbrack i\rbrack}} \right)/\left( {2 \times {frame\_ rate}} \right)}} +}} \\{\quad {{decode\_ start}{\_ up}{\_ delay}}}\end{matrix}$

[0296] If the GOP length is N and the intervals of P-pictures is M, themaximum value of the number of pictures Ndec to be decoded from theleading picture Pfirst up to the in-point picture Pin is given by thefollowing equation (20):

Ndec=N+M−1  (20).

[0297] From the above equations (19) and (20), the maximum value of theterm T3 T3_max is given by the equation (21): $\begin{matrix}{\begin{matrix}{{T3} = \quad {{\sum\limits_{i = 0}^{N + {M\quad \_ 1}}{\left( {2 + {{rff}\lbrack i\rbrack}} \right)/\left( {2 \times {frame\_ rate}} \right)}} +}} \\{\quad {{decode\_ start}{\_ up}{\_ delay}}}\end{matrix}.} & (21)\end{matrix}$

[0298] It is noted that decode start_up_delay=1.75 mbit/Rpg_max. If thei'th picture is a B-picture, rff[i] is a value of repeat_first_field ofthe picture. If the i'th picture is an I-picture or a P-picture, rff[i]is a value of repeat_first_field of the previous I- or P-picture.

[0299] During the T3 period, two programs, namely the out-point sideprogram and the in-point side program, are outputted from the mainbuffer 21 at a rate of 2*Rpg_max at the maximum. The main buffer 21 isrequired to have such a capacity as to supply the out-point side programand the in-point side program without underflowing during the period ofT3_max. That is, the capacity MB_size of the main buffer 21 is given bythe following equation (22):

MB_size=T3_max×(2×Rpg_max−Rin)=T3_max×(Rpg_max−α)  (22).

[0300] The time length of the term T1 is the time which elapses untilthe bit occupying volume of the main buffer 21 is varied from 0 toMB_size in a state in which the video decoding unit 49 is decoding theout-point side program or the in-point side program at the normaldecoding speed, and is given by the equation (23):

T1=MB_size/(Rin−Rpg_max)=MB_size/α  (23).

[0301] If skipping reproduction is to be repeated on end, there is anecessary minimum time length from the in-point picture to the nextout-point picture, so that limitations are imposed on the positions ofthe in-point picture and the out-point picture. The reason is that themain buffer 21 needs to be charged to its full capacity to performskipping reproduction. That is, the minimum necessary time Lmin forskipping reproduction from the in-point picture to the next out-pointpicture is given by the equation (24):

Lmin=T1  (24).

[0302] In the optical disc recording/reproducing apparatus of thepresent second embodiment, the out-point side program and the in-pointside program are time-divisionally decoded by a sole decoding unit at adouble speed in order to output on end an out-point picture whosedisplay is completed at PTS_Pout_end and the in-point picture whichstarts to be displayed at PTS_Pin, whilst the STC is reset fromPTS_Pout_end to PTS_Pin at a switching timing from the out-point pictureto the in-point picture. This enables the present optical discrecording/reproducing apparatus 1 to effect seamless skippingreproduction as continuity is upheld before and after the switchingpoint.

[0303] In the optical disc recording/reproducing apparatus of thepresent second embodiment, advance decision of possibility of seamlessreproduction can be made as in the above-described optical discrecording/reproducing apparatus of the first embodiment.

[0304] In the above-described first embodiment, there is shown anexample in which the out-point side program and the in-point sideprogram are processed in parallel using two decoding units, whereas, inthe second embodiment, there is shown an example in which the out-pointside program and the in-point side program are processed in parallelusing a sole decoding unit which performs time-divisional processing ata double decoding speed. The present invention, however, is not limitedto this system and may be applied to such a decoding device in which theabove-described first and second embodiments are combined such as toprocess the out-point side program and the in-point side program inparallel. For example, although a number of internal processing unitsare provided in a decoding device adapted for decoding encoded data ofthe MPEG system, it is also possible to effect IDCT by two processingunits and to effect the variable length decoding time-divisionally by asole processing unit.

Third Embodiment

[0305] A recording/reproducing apparatus for an optical disc accordingto a third embodiment of the present invention is hereinafter explained.In this third embodiment, similarly to the second embodiment, only thestructure of the decoding device is modified from that of the decodingdevice 10 of the above-described first embodiment. That is, the presentoptical disc recording/reproducing apparatus is the same as theapparatus of the first embodiment except the structure of the decodingdevice 10. Therefore, only a decoding device associated with thisdecoding device 10 is explained in detail. The component parts which arethe same as those of the decoding device 10 of the first embodiment andthe decoding device 40 of the second embodiment are depicted by the samereference numerals and are not explained specifically.

[0306] The decoding device of the optical disc recording/reproducingapparatus of the third embodiment of the present invention is explainedin detail.

[0307]FIG. 24 shows a block diagram of a decoding device applied to theoptical disc recording/reproducing apparatus of the present thirdembodiment. A decoding device 60 shown in FIG. 24 is used in place ofthe decoding device 10 of the first embodiment of therecording/reproducing apparatus shown in FIG. 3.

[0308] Referring to FIG. 24, the decoding device 60 includes a mainbuffer 21 for temporarily storing multiplexed data made up of video dataand audio data sent from the buffer 6 (FIG. 3), and a separation unit 61for extracting the bitstream stored in the main buffer 21 to separate abitstream of the out-point side program and a bitstream of the in-pointside program during skipping reproduction. The decoding device 60 alsoincludes a switching unit 62 for time-divisionally switching between thebitstreams of the AV program extracted by the separation unit 61 forseparation into the video bitstream and the audio bitstream.

[0309] The decoding device 60 also includes a video buffer 63 forstoring a video bitstream and an audio buffer 64 for storing an audiobitstream.

[0310] The decoding device 60 additionally includes a video decodingunit 70 for extracting and decoding a video bitstream stored in thevideo buffer 63, an audio decoding unit 50 for extracting and decodingan audio bitstream stored in the audio buffer 64, a display controller67 for controlling the output timing of the video and audio data and atiming controller 37 for generating system time clocks as the referencesynchronization signal of the present system.

[0311] The main buffer 21 is fed from the buffer 6 (FIG. 3) with abitstream of video and audio data multiplexed on the package basis at abitrate of Rin. This bitstream is temporarily stored in the main buffer21 and subsequently extracted by the separation unit 61 at a presettiming. The writing in the main buffer 21 is halted when it is chargedto its capacity.

[0312] In this main buffer 21 are stored video and audio data of a soleAV program during normal reproduction. During skipping reproduction, thetwo AV programs, namely the out-point side program and the in-point sideprogram, are read out from the optical disc 2 so as to be stored in themain buffer 21.

[0313] The separation unit 61 extracts the bitstream of the multiplexedvideo and audio data from the main buffer 21 at a bitrate of Rout.During skipping reproduction, the separation unit 61 extracts data ofthe out-point side program stored in the main buffer 21 and subsequentlyextracts data of the in-point side program. At this time, the separationunit 61 extracts the video and audio data during skipping reproductionbased on the playback control information sent from the playbackcontroller 8 (FIG. 3). This extraction is executed on the basis of theindex (P_last_index) of the last picture Plast of the playback controlinformation of the out-point side program or the index (P_in_index) ofthe in-point picture Pin of the playback control information of thein-point side program. The separation unit 61 sends the extracted datato the switching unit 62. The separation unit 61 also extracts thesystem header contained in the multiplexed data of the out-point sideprogram and the in-point side program to send this system header to thedisplay controller 67.

[0314] The switching unit 62 time-divisionally separates the bitstreamof the video and audio data multiplexed in the out-point side programand in the in-point side program to provide a bitstream only of videodata and a bitstream only of audio data. The video bitstream of theout-point side program and the video bitstream of the in-point sideprogram, separated by the switching unit 62, are sent to the videobuffer 63. The audio bitstream of the out-point side program and theaudio bitstream of the in-point side program, separated by the switchingunit 62, are sent to the audio decoding unit 50.

[0315] The video buffer 63 transiently stores the audio bitstream sentfrom the switching unit 62. The video bitstream stored in the videobuffer 63 is extracted to the video decoding unit 70 at a preset timing.

[0316] The audio buffer 64 transiently stores the video bitstream sentfrom the switching unit 62. The audio bitstream stored in the audiobuffer 64 is extracted to the audio decoding unit 50 in synchronism withthe video decoding timing.

[0317] The video decoding unit 70 decodes the video bitstream encodedfor compression in accordance with MPEG 2 system to generate digitalpicture data. This video decoding unit 70 decodes the pictures at aspeed faster than the picture display speed. This video decoding unit 70has a decoding speed twice the minimum decoding speed necessary forreal-time display of video data supplied in real-time. During normalreproduction, this video decoding unit 70 decodes the pictures at anormal decoding speed in accordance with the decoding time stamp DTSaffixed to each picture. On the other hand, during skippingreproduction, the video decoding unit 70 decodes the out-point sideprogram and the in-point side program at a decoding speed twice theusual decoding speed in negligence of the DTS. The digital picture data,decoded by this video decoding unit 70, is stored in a frame memory 65.

[0318] The audio decoding unit 50 decodes the audio bitstream encodedfor compression in accordance with the MPEG 2 system to generate digitalspeech data. The digital speech data, decoded by the audio decoding unit50, is stored in an audio memory 66. Similarly to the video decodingunit 70, the audio decoding unit 50 is designed to decode audio data ata speed faster than the speech output speed.

[0319] The frame memory 65 is a memory for transient storage of thedecoded pictures on the picture basis. Specifically, this frame memory65 has the function of storing a picture which has been decoded butwhich has not as yet been displayed in case the video decoding unit 70executes decoding at a speed faster than the usual display speed.

[0320] The audio memory 66 transiently stores decoded audio data.Specifically, this audio memory 66 has the function of storing speechdata which has been decoded but which has not as yet been displayed incase the audio decoding unit 67 executes decoding at a speed faster thanthe usual speech outputting speed.

[0321] The display controller 67 controls the output timing of eachpicture decoded by the video decoding unit 70 and speech data decoded bythe audio decoding unit 50 based on the playback control informationsupplied from the playback controller 8 (FIG. 3) and the STC sent fromthe timing controller 37.

[0322] Specifically, the display controller 67 outputs each picturedecoded by the video decoding unit 70 when the STC generated by thetiming controller 37 coincides with the presentation time stamp PTS(temporal management information) of the playback output affixed to eachpicture. During skipping reproduction, this display controller 67switches an output picture from the out-point side program to thein-point side program at a display switching timing between theout-point picture of the out-point side program and the in-point pictureof the in-point side program.

[0323] The display controller 67 also outputs speech data in synchronismwith picture data outputted by the video decoding unit 70. The displaycontroller 67 also switches output audio data from the out-point sideprogram to the in-point side program at a display switching timingbetween the out-point picture of the out-point side program and thein-point picture of the in-point side program.

[0324] The bitrate of the bitstream supplied from the main buffer 21 andthat of the bitstream read out from the main buffer 21 are assumed to beRin and Rout, respectively. The bitrate of the video bitstream sent tothe video buffer 63, that of the audio bitstream sent to the audiobuffer 64 and that of the system header sent from the separation unit 61are assumed to be Rv, Ra and Rsys, respectively. The sum of Rv, Ra andRsys is assumed to be the program bitrate Rpg and the maximum value ofRpg is assumed to be Rpg_max.

[0325] If the respective bitrates are defined as above, the followingrelation:

Rin=Rpg−max+α(α>0) rout≦2×Rpg_max  (25)

[0326] holds, where Rin is the bitrate of the bitstream sent to the mainbuffer 21 and Rpg_max is the maximum bitrate, respectively, and α takesaccount of delay time on startup of the video decoding unit 70.

[0327] The processing during skipping reproduction of the decodingdevice 60 is now explained with reference to the flowchart of FIGS. 25to 27.

[0328]FIG. 25 shows the contents of the reading of a datastream of themain buffer 21 at the time of skipping from the out-point side programto the in-point side program. It is noted that this reading processingof the main buffer 21 is controlled by a buffer manager, not shown.

[0329] First, at step SP61, it is checked whether or not there is anyavailable vacant area in the main buffer 21. The processing is at astandstill at this step SP61 until a vacant area in the main buffer 21is available.

[0330] If there is produced any available vacant area in the main buffer21, the out-point side program is read into the main buffer 21 at thenext step SP62.

[0331] At the next step SP63, it is checked whether or not the last byteof the out-point side program has been read. If the last byte of theout-point side program has not been read, the processing as from stepSP61 is repeated. If it is determined at this step SP63 that the lastbyte of the out-point side program has been read, processing transfersto step SP64.

[0332] At step SP64, it is checked whether or not there is any availablevacant area in the main buffer 21. The processing is at a standstill atthis step SP64 until a vacant area in the main buffer 21 is available.

[0333] If there is produced any available vacant area in the main buffer21, the in-point side program is read into the main buffer 21.

[0334] The processing comes to a close when the in-point side program isread in its entirety. If the decoding device 10 repeats the processingof skipping reproduction, the processing as from the step SP61 isrepeated.

[0335] By the above processing form step SP61 to step SP65, the decodingdevice 60 can read-in data into the main buffer 21 at the time ofskipping reproduction.

[0336]FIGS. 26 and 27 show the contents of decoding and outputtingprocessing by the decoding device 60.

[0337] When the skipping reproduction processing is started, the timingcontroller 37 sets the STC (system time clock) to the SCR (system clockreference) of the out-point side program at step SP71 shown in FIG. 26.

[0338] At the next step SP72, if there is any available vacant areaavailable in the frame memory 65, the video decoding unit 70 reads outpictures of the out-point side program from the video buffer 63 todecode the pictures at e.g., a double decoding speed, in negligence ofthe decoding time stamp (DTS) of each picture, to store the decodedpicture in the frame memory 65.

[0339] At the next step SP73, the display controller 67 displays thepictures of the out-point side program, decoded by the video decodingunit 70, in accordance with its DTS.

[0340] At the next step SP74, it is checked whether or not decoding ofthe out-point picture of the out-point side program has come to a close.If decoding of the out-point picture of the out-point side program hasnot come to a close, processing as from step SP72 is repeated. If, atthis step SP74, it is found that the decoding of the out-point pictureof the out-point side program has come to a close, processing transfersto step SP75.

[0341] At this step SP75, the display controller 67 causes each pictureof the out-point side program decoded by the video decoding unit 70 tobe displayed in accordance with its DTS.

[0342] At step SP76, the video decoding unit 70 reads out the picturesof the in-point side program from the video buffer 63 to decode theread-out pictures at e.g., a double decoding speed in negligence of theDTS of each picture.

[0343] At the next step SP77, it is checked whether or not decoding ofthe in-point side program has come to a close. If it is determined thatthe decoding of the in-point picture has come to a close, processingtransfers to step SP78.

[0344] At step SP78, it is determined whether or not the picture type ofthe in-point picture is an I-picture or a P-picture. This decision isgiven based on P-in-type indicated in the playback control information.If the in-point picture is the I- or P-picture, the video decoding unit70 reads and discards the in-point side program stored in the videobuffer 63 up to the next I- or P-picture before processing transfers tostep SP80 shown in FIG. 27. If the in-point picture is not an I-picturenor a P-picture, processing directly transfers to step SP80 shown inFIG. 27.

[0345] At step SP80, shown in FIG. 27, the decoded in-point picture isstored in the frame memory 65.

[0346] At the next step SP81, it is checked whether or not the STC isequal to PTS_Pout_end, that is whether or not display of the out-pointpicture has come to a close.

[0347] If the STC is not PTS_Pout_end, the display controller 67continues to output each picture of the decoded out-point side programin accordance with its PTS. The processing of this step SP82 iscontinued until the STC is equal to PTS_Pout_end.

[0348] If the STC is equal to PTS_Pout_end, the in-point picture decodedby the video decoding unit 70 is displayed at step SP83, at the sametime as the STC is reset in PTS_Pin.

[0349] At the next step SP84, if there is any available vacant area inthe frame memory 65, the video decoding unit 70 decodes the in-pointside program stored in the video buffer 63 at e.g., a double decodingspeed, in negligence of the DTS stored in the video buffer 63, to storethe decoded picture in this frame memory 65. Simultaneously, the displaycontroller 67 displays at step SP84 each picture of the in-point sideprogram decoded by the video decoding unit 70 in accordance with itsPTS.

[0350] By the processing of from step SP71 to step SP84 as describedabove, the video decoding unit 70 can decode the out-point side programand the in-point side program at the time of skipping reproduction. Onthe other hand, by the processing of from step SP71 to step SP84, thedisplay controller 67 can output the out-point side program and thein-point side program at the time of skipping reproduction.

[0351] In MPEG 2 system, 2-3 pull-down processing of repeatedlyoutputting a pre-set field on end is performed in consideration that themotion picture film is made up of 24 picture frames per second. Fromthis, if 2-3 pull-down is not performed at the out-point picture, thePTS_Pout_end is equal to PTS_Pout plus one-frame time, whereas, if 2-3pull-down is performed at the out-point picture, the PTS_Pout_end isequal to PTS_Pout plus three-field time.

[0352] Thus, by performing the processing shown in FIGS. 25 to 27, it ispossible with the optical disc recording/reproducing apparatus tomaintain continuity of the moving picture before and after skippingreproduction.

[0353] The decoding and display timing in the decoding device 60 isexplained taking an example of reproducing the out-point side programshown in FIG. 28A up to B₀₇, then skipping and reproducing the in-pointside program from P_(n5).

[0354] Referring to FIG. 28B, the video decoding unit 70 sequentiallydecodes the out-point side program as from time t⁻⁹ to decode B₀₇ (lastpicture Plast) at time point t⁻³ to terminate the decoding of theout-point side program. The video decoding unit 70 sequentially decodesthe in-point side program, since time point t⁻³, to complete thedecoding up to B_(n4) at time t₀. The video decoding unit 70 operates ata double speed since time point t⁻⁶ until time point t⁻⁰ to decode theout-point side program and the in-point side program. Specifically, thevideo decoding unit 70 decodes the pictures from P₀₅ until B₀₇ of theout-point side program since time point t⁻⁶ until time point t⁻³, whiledecoding pictures I_(n2) to B_(n5) of the in-point side program sincetime t⁻³ until time t₀ to terminate the decoding before t₀ to completedecoding of P_(n5) as the in-point picture. Meanwhile, as to picturesfrom I_(n2) to B_(n4) of the in-point side program, only I- andP-pictures are decoded, while it is unnecessary to decode theB-pictures. The reason is that the pictures from I_(n2) up to B_(n4) arenot displayed and only I- and P-pictures are required for decodingP_(n5) (in-point picture).

[0355] The video decoding unit 70 also displays the decoded out-pointside program until time point to in accordance with its PTS, as shown inFIG. 28C. At the time point t₀ when display of the out-point picturePout comes to a close, the STC is reset to a value of PTS_Pin, while thedecoded in-point side program is sequentially displayed in accordancewith the PTS of each picture, as shown in FIG. 28E.

[0356] By decoding and display in this manner, the decoding device 60can continuously display the out-point and in-point pictures to effectseamless reproduction of the out-point side program and the in-pointside program, as shown in FIG. 28F.

[0357] The transition of the bit occupying volume of the main buffer 21and the video buffer 63 during skipping reproduction is explained withreference to FIG. 29.

[0358]FIG. 29A shows the bit occupying volume of multiplexed data in themain buffer 21. This bit occupying volume is varied from MB_size as thecapacity of the main buffer 21 to 0. FIG. 29B shows the bit occupyingvolume of the video bitstream of the video buffer 63. This bit occupyingvolume is varied from the capacity of the video buffer 63 to 0.

[0359] The term T1 denotes the state in which the video decoding unit 70is decoding the out-point side program at a normal decoding speed. Theoutput bitrate of the main buffer 21 is Rpg. The bit occupying volume ofthe main buffer 21 increases up to the full state at a rate ofα(Rin−Rpg).

[0360] During the term T2, the out-point side program is decoded by thevideo decoding unit 70. At this time, the video decoding unit 70performs decoding at a double decoding speed if there is any availablevacant area in the frame memory 65. During the term T2, the maximumvalue of the output bitrate of the main buffer 21 is 2Rpg. The bitoccupying volume of the main buffer 21 is decreased at a rate of Rpg−α.

[0361] During the term T3, the out-point side program is decoded by thevideo decoding unit 70 at the normal decoding rate, as during the termT1. Thus, the maximum value of the output bitrate of the main buffer 21during the term T3 is Rpg. The bit occupying volume of the main buffer21 is increased at a rate of α until the full state is reached.

[0362] During the term T4, decoding of the in-point side program isstarted by the video decoding unit 70 at a double rate. Therefore, themaximum value of the output bitrate of the main buffer 21 during theterm T4 is 2Rpg. Thus, the bit occupying volume of the main buffer 21 isdecreased at a rate of Rpg−α. If the decoding of the in-point picturecomes to a close, the video decoding unit 70 is halted transiently.

[0363] During the term T5, the video decoding unit 70 decodes thein-point side program at a normal decoding speed. Therefore, the maximumvalue of the output bitrate of the main buffer 21 during the term T5 isRpg. The bit occupying volume of the main buffer 21 is increased at arate of α.

[0364] During the term T6, the video decoding unit 70 is decoding thein-point side program. If, at this time, there is any vacant availablearea in the frame memory 65, the video decoding unit 70 decodes theprogram at a double decoding speed. The maximum value of the outputbitrate of the main buffer 21 during the term T6 is 2Rpg. The bitoccupying volume of the main buffer 21 is decreased at a rate of Rpg−α.

[0365] During the term T7, the video decoding unit 70 decodes thein-point side program at a normal decoding speed, as during the term T1.Therefore, the maximum value of the output bitrate of the main buffer 21during the term T6 is Rpg. The bit occupying volume of the main buffer21 is increased at a rate of α until the full state is reached.

[0366] During the term T4, there is produced a pre-set delay time fordecoding the initial picture by the video decoding unit 70. This delaytime is assumed to be decode start-up delay (decode_start_up_delay).

[0367] Then, respective parameters required for seamless skippingreproduction are found in consideration of the bit occupying volumes,for example, of the respective memories.

[0368] For resetting the STC at time point to, the offset timeSTC_offset, applied to the STC, is set as shown by the equation (26):

STC_offset=PTS_Pout_end−PTS_Pin  (26).

[0369] The time length of T4 is the time since start of supply of thein-point side program to the VES buffer 13 until end of the in-pointside program when the frame memory 65 is operating at a double speed. IfN is the GOP length and M is an interval of the I- or P-pictures, themaximum value of T4 is given by the equation (27):

T4_max=((N+m−1)/frame_rate)/2+decode_start_up_delay  (27).

[0370] Meanwhile, this decode_start_up_delay is 1.75 Mbit/(3Rpg).

[0371] If, for example, M=15 and M=3, the maximum value of T4corresponds to a case in which the in-point picture is B₁ which is thefirst B-picture of the GOP. That is, in such case, the GOP directlyprevious to the GOP containing the in-point side program needs to bedecoded in its entirety. In this case, the time length of T4 is given bythe equation (28):

T4_max=((17)/frame_rate)/2+decode_start_up_delay  (28).

[0372] The number of frames (Nf) required for the frame memory 65depends on the time length of T4 and is represented by the equation(29):

Nf=T4_max/frame_rate  (29).

[0373] The time length of T2 9or T60 is such time length during which2Nf pictures are decoded at a double decoding speed and stored in theframe memory 65. The time length of T2 (or T6) is as shown by thefollowing equation (30):

T2=T6=2Nf/2frame_rate=Nf/frame_rate  (30).

[0374] The main buffer 21 is required to have a minimum capacitysufficient to read-in a bitstream such as to decode the in-point sideprogram at a double decoding speed without underflowing of the in-pointside program. Therefore, the capacity (MB_size) of the main buffer 21 isgiven b the following equation (31):

Tmax=max(T4_max, T2) MB_size=Tmax×(2Rpg−Rin)=Tmax×(Rpg−α)  (31).

[0375] The time length of T1 (also, T3 or T7), which is the time duringwhich the bit occupying volume of the main buffer 21 reaches the fulstate from the zero state, is given by the following equation (32):

T1=MB_size/(Rin−Rpg)=MB_size/α  (32).

[0376] The minimum necessary time for continuous skipping reproductionfrom the in-point picture up to the out-point picture is the time asshown by the following equation (33):

Lmin=T1+Tmax

[0377] With the above-described third embodiment of therecording/reproducing apparatus of the present invention, encoded dataof the MPEG system are decoded by the video decoding unit 70 at a speedfaster than the display speed, an out-point picture whose display iscompleted with PTS_Pout_end and an in-point picture which starts to bedisplayed with PTS_Pin are outputted continuously and the STC is resetfrom PTS_Pout_end to PTS_Pin at a switching timing from the out-pointpicture to the in-point picture. This enables the optical discrecording/reproducing apparatus to realize seamless skippingreproduction as continuity is upheld before and at back of the switchingpoint.

What is claimed is:
 1. A decoding apparatus for data of moving picturesfor decoding encoded data of moving pictures encoded using a predictiveencoding system, comprising: decoding means for decoding first encodeddata made up of moving pictures up to a preset moving picture and secondencoded data made up of moving pictures beginning from a moving picturedisplayed next to the preset moving picture at a speed faster than thedisplay speed of the encoded data; and output control means forcontrolling the outputting of decoded moving pictures based on the timemanagement information of each moving picture of said encoded data. 2.The decoding apparatus for data of moving picture according to claim 1wherein the output control means change reference synchronizationsignals to a second time point when the reference synchronizationsignals are equal to a first time point to output moving picturesbeginning from a moving picture displayed at said second time point. 3.The decoding apparatus for data of moving picture according to claim 1wherein said decoding means time-divisionally decode said first encodeddata and the second encoded data.
 4. The decoding apparatus for data ofmoving picture according to claim 1 further comprising: storage meansfor transiently storing the moving picture data decoded by said decodingmeans; said decoding means decoding said first encoded data andsubsequently decoding said second encoded data beginning from a movingpicture which starts to be displayed at a time point skipped a presettime interval from said first time point.
 5. The decoding apparatus fordata of moving picture according to claim 1 wherein said decoding stepdecodes encoded data of moving pictures encoded using the MPEG (MovingPicture Experts Group) system.
 6. A decoding method for data of movingpictures for decoding encoded data of moving pictures encoded using apredictive encoding system, comprising: a decoding step for decodingfirst encoded data made up of moving pictures up to a preset movingpicture and second encoded data made up of moving pictures beginningfrom a moving picture displayed next to said preset moving picture at aspeed faster than the display speed of the encoded data; and an outputcontrol step for controlling the outputting of decoded moving picturesbased on the time management information of each moving picture of saidencoded data.
 7. The decoding method for data of moving pictureaccording to claim 6 wherein the output control step changes referencesynchronization signal to a second time point when the referencesynchronization signal is equal to a first time point to output movingpictures beginning from a moving picture displayed at said second timepoint.
 8. The decoding method for data of moving picture according toclaim 6 wherein said decoding step time-divisionally decode said firstencoded data and the second encoded data.
 9. The decoding method fordata of moving picture according to claim 6 further comprising: astorage step for transiently storing the moving picture data decoded bysaid decoding step; said decoding step decoding said first encoded dataand subsequently decoding said second encoded data beginning from amoving picture which starts to be displayed at a time point skipped apreset time interval from said first time point.
 10. The decoding methodfor data of moving picture according to claim 6 wherein said decodingstep decodes encoded data of moving pictures encoded using the MPEG(Moving Picture Experts Group) system.
 11. A decoding apparatus for dataof moving picture for decoding encoded data of moving pictures encodedusing a predictive encoding system, comprising: first decoding means fordecoding encoded data up to a moving picture whose display is completedat a first time point corresponding to a preset display time point;second decoding means for decoding encoded data beginning from a movingpicture which starts to be displayed at a second time point skipped apreset time interval from said first time point; output control meansfor controlling the outputting of a moving picture decoded by said firstdecoding means or said second decoding means when the time managementinformation of said encoded data coincides with referencesynchronization signals; and switching means for changing said referencesynchronization signals to said second time point when the referencesynchronization signals are equal to said first time point for switchingthe moving picture output-controlled by said output control means to thepicture decoded by said second decoding means.
 12. The decodingapparatus for data of moving picture according to claim 11 wherein saidsecond decoding means decodes encoded data required in case of decodingthe moving picture which starts to be displayed at said second timepoint up to a picture displayed at said second time point before saidfirst time point.
 13. The decoding apparatus for data of moving pictureaccording to claim 11 wherein said first decoding means and the seconddecoding means decode encoded data of moving pictures encoded using theMPEG (Moving Picture Experts Group) system.
 14. A decoding method fordata of moving picture for decoding encoded data of moving picturesencoded using a predictive encoding system, comprising: a first decodingstep for decoding encoded data up to a moving picture whose display iscompleted at a first time point corresponding to a preset display timepoint; a second decoding step for decoding encoded data beginning from amoving picture which starts to be displayed at a second time pointskipped a preset time interval from said first time point; an outputcontrol step for generating a reference synchronization signal and forcontrolling the outputting of a moving picture decoded by said firstdecoding step or said second decoding step when the time managementinformation coincides with reference synchronization signals; and aswitching step for changing said reference synchronization signal tosaid second time point when the reference synchronization signal isequal to said first time point for switching the moving pictureoutput-controlled by said output control step to the picture decoded bysaid second decoding step.
 15. The decoding method for data of movingpicture according to claim 14 wherein said second decoding step decodesencoded data required in case of decoding the moving picture whichstarts to be displayed at said second time point up to a picturedisplayed at said second time point before said first time point. 16.The decoding method for data of moving picture according to claim 14wherein said first decoding step and the second decoding step decodeencoded data of moving pictures encoded using the MPEG (Moving PictureExperts Group) system.
 17. A recording apparatus for moving picture datacomprising: encoding means for encoding moving picture data using apredictive encoding system; designation information supplying means forsupplying the information designating a decoding starting picture and adisplay starting picture in said moving picture data and for supplyingthe information designating a decoding terminating picture and a displayterminating picture in said moving picture data; and recording means forrecording moving picture data encoded by said encoding means and thedesignation information supplied by said designation informationsupplying means.
 18. The recording apparatus according to claim 17wherein said encoding means encodes the position of a leading data byteof a decoding starting picture on an encoding data file of movingpictures as the information designating the decoding starting picture ina reproducing unit of the moving picture data.
 19. The recordingapparatus according to claim 17 wherein said encoding means encodes adisplay start time point of the display starting picture as theinformation designating the decoding starting picture in a reproducingunit of the moving picture data.
 20. The recording apparatus accordingto claim 17 wherein said encoding means encodes the position of the lastdata byte of a decoding terminating picture on an encoding data file ofmoving pictures as the information designating the decoding terminatingpicture in a reproducing unit of the moving picture data.
 21. Therecording apparatus according to claim 17 wherein said encoding meansencodes a display termination time point of a display terminatingpicture as the information designating the decoding starting picture ina reproducing unit of the moving picture data.
 22. The recordingapparatus according to claim 17 wherein said encoding means encodes adisplay start time point of a display terminating picture as theinformation designating the decoding terminating picture in areproducing unit of the moving picture data.
 23. A recording method formoving picture data comprising: encoding means for encoding movingpicture data using a predictive encoding system; supplying theinformation designating a decoding starting picture and a displaystarting picture in said moving picture data and for supplying theinformation designating a decoding terminating picture and a displayterminating picture in said moving picture data; and recording encodedmoving picture data and the supplied designation information.
 24. Therecording method for moving picture data according to claim 23 furthercomprising: encoding the position of a leading data byte of a decodingstarting picture on an encoding data file of moving pictures as theinformation designating a decoding starting picture in a reproducingunit of the moving picture data.
 25. The recording method for movingpicture data according to claim 23 further comprising: encoding adisplay start time point of the display starting picture as theinformation designating the display starting picture in a reproducingunit of the moving picture data.
 26. The recording method according toclaim 23 further comprising: encoding the position of the last data byteof a decoding terminating picture on an encoding data file of movingpictures as the information designating the decoding terminating picturein a reproducing unit of the moving picture data.
 27. The recordingmethod according to claim 23 further comprising: encoding a displaytermination time point of a display terminating picture as theinformation designating the decoding starting picture in a reproducingunit of the moving picture data.
 28. The recording method according toclaim 23 further comprising: encoding a display start time point of adisplay terminating picture as the information designating the decodingterminating picture in a reproducing unit of the moving picture data.29. A recording medium on which there are recorded the informationdesignating a decoding starting picture and a display starting picturein moving picture data and the information designating a decodingterminating picture and a display terminating picture in moving picturedata along with encoded data of moving pictures encoded using thepredictive encoding system.
 30. The recording medium according to claim29 wherein the position of a leading data byte of a decoding startingpicture on an encoding data file of moving pictures is recorded thereonas the information designating the decoding starting picture in areproducing unit of the moving picture data.
 31. The recording mediumaccording to claim 29 wherein a display start time point of the displaystarting picture is recorded thereon as the information designating thedecoding starting picture in a reproducing unit of the moving picturedata.
 32. The recording medium according to claim 29 wherein theposition of the last data byte of a decoding terminating picture on anencoding data file of moving pictures is recorded thereon as theinformation designating the decoding terminating picture in areproducing unit of the moving picture data.
 33. The recording mediumaccording to claim 29 wherein a display termination time point of adisplay terminating picture is recorded thereon as the informationdesignating the display terminating picture in a reproducing unit of themoving picture data.
 34. The recording medium according to claim 29wherein a display start time point of a display terminating picture isrecorded thereon as the information designating the decoding terminatingpicture in a reproducing unit of the moving picture data.
 35. A decodingapparatus for moving picture data comprising: decoding means fordecoding encoded data of moving pictures encoded using a predictiveencoding system; and control means for controlling the decoding and theoutputting of moving picture data by said decoding means based on theinformation designating a decoding start picture and a display startpicture in moving picture data and on the information designating adecoding terminating picture and a display terminating picture in saidmoving picture data.
 36. The decoding apparatus for moving picture dataaccording to claim 35 wherein said control means controls the decodingand the outputting of moving picture data by said decoding means basedon the position of a leading data byte of a decoding start picture on anencoding data file of moving pictures indicated as the informationspecifying a decoding starting picture in a reproducing unit of movingpicture data.
 37. The decoding apparatus for moving picture dataaccording to claim 35 wherein said control means controls the decodingand the outputting of moving picture data by said decoding means basedon a display starting time point of a display starting picture indicatedas the information designating a display starting picture in areproducing unit of moving picture data.
 38. The decoding apparatus formoving picture data according to claim 35 wherein said control meanscontrols the decoding and the outputting of moving picture data by saiddecoding means based on the position of the last data byte of a decodingterminating picture on an encoding data file of moving picturesindicated as the information specifying a decoding terminating picturein a reproducing unit of moving picture data.
 39. The decoding apparatusfor moving picture data according to claim 35 wherein said control meanscontrols the decoding and the outputting of moving picture data by saiddecoding means based on a display end time point of a displayterminating picture indicated as the information specifying the displayterminating picture in a reproducing unit of moving picture data. 40.The decoding apparatus for moving picture data according to claim 35wherein said control means controls the decoding and the outputting ofmoving picture data by said decoding means based on a display startingtime point of a display terminating picture indicated as the informationspecifying the display terminating picture in a reproducing unit ofmoving picture data.
 41. A decoding method for moving picture datacomprising: decoding encoded data of a moving picture encoded using apredictive encoding system based on the information specifying adecoding starting picture and a display starting picture in movingpicture data and on the information specifying a decoding terminatingpicture and a display terminating picture in moving picture data; andoutputting the decoded data.
 42. The decoding method for moving picturedata according to claim 41 comprising: decoding encoded data of movingpicture data encoded by a predictive encoding system based on theposition of a leading data byte of a decoding start picture on anencoding data file of moving pictures indicated as the informationspecifying a decoding starting picture in a reproducing unit of movingpicture data; and outputting the decoded data.
 43. The decoding methodfor moving picture data according to claim 41 comprising: decodingencoded data of moving picture data encoded by a predictive encodingsystem based on a display starting time point of a display startingpicture indicated as the information designating a display startingpicture in a reproducing unit of moving picture data; and outputting thedecoded data.
 44. The decoding method for moving picture data accordingto claim 41 comprising: decoding encoded data of moving picture dataencoded by a predictive encoding system based on the position of thelast data byte of a decoding terminating picture on an encoding datafile of moving pictures indicated as the information specifying adecoding terminating picture in a reproducing unit of moving picturedata; and outputting the decoded data.
 45. The decoding method formoving picture data according to claim 41 comprising: decoding encodeddata of moving picture data encoded by a predictive encoding systembased on a display end time point of a display terminating pictureindicated as the information specifying the display terminating picturein a reproducing unit of moving picture data; and outputting the decodeddata.
 46. The decoding method for moving picture data according to claim41 comprising: decoding encoded data of moving picture data encoded by apredictive encoding system based on a display starting time point of adisplay terminating picture indicated as the information specifying thedisplay terminating picture in a reproducing unit of moving picturedata; and outputting the decoded data.
 47. A continuous reproductionpossibility verifying apparatus for encoded data wherein in reproducinga series of encoded data encoded using a predictive encoding system bydecoding pictures of said encoded data from a first display startingpoint picture of said encoded data to a first display terminating pointpicture of said encoded data, designated as an out-point picture inskipping processing of said encoded data, then skipping the decodingfrom said first display terminating point picture to a second displaystarting point picture designated as an in-point picture in saidskipping processing, and by decoding pictures from said second displaystarting point picture to a second display terminating point picture, itis verified, based on the time difference between a display time pointof said first display starting point picture and a display time point ofsaid first display terminating point picture, whether or not continuousdisplay of said first display terminating point picture and said seconddisplay starting point picture is possible.
 48. The continuousreproduction possibility verifying apparatus for encoded data accordingto claim 47 wherein storage time during which said encoded data requiredfor decoding said second display starting point picture is stored inmemory means after being read out from a recording medium prior tooutputting to decoding means is calculated, based on the volume of saidencoded data required for decoding said second display starting pointpicture and the bitrate of said encoded data; said time differencebetween the display time point of said first display starting pointpicture and the display time point of said first display terminatingpoint picture is compared to said storage time; it is verified thatcontinuous display of said first display terminating point picture andsaid second display starting point picture is possible if said timedifference is not less than said storage time; and it is verified thatcontinuous display of said first display terminating point picture andsaid second display starting point picture is not possible if said timedifference is less than said storage time.
 49. The continuousreproduction possibility verifying apparatus for encoded data accordingto claim 47 wherein said encoded data is obtained on encoding using theMPEG (Moving Picture Experts Group) system.
 50. A continuousreproduction possibility verifying apparatus for encoded data wherein inreproducing a series of encoded data encoded using a predictive encodingsystem by decoding pictures of said encoded data from a first displaystarting point picture of said encoded data to a first displayterminating point picture of said encoded data, designated as anout-point picture in skipping processing of said encoded data, thenskipping the decoding from said first display terminating point pictureto a second display starting point picture designated as an in-pointpicture in said skipping processing, and by decoding pictures from saidsecond display starting point picture to a second display terminatingpoint picture, it is verified, based on the time difference between adisplay time point of said first display starting point picture and adisplay time point of said first display terminating point picture,whether or not continuous display of said first display terminatingpoint picture and said second display starting point picture ispossible.
 51. The continuous reproduction possibility verifying methodfor encoded data according to claim 50 comprising: calculating thestorage time during which said encoded data required for decoding saidsecond display starting point picture is stored after being read outfrom a recording medium in memory means prior to outputting to decodingmeans, based on the volume of said encoded data required for decodingsaid second display starting point picture and the bitrate of saidencoded data; comparing said time difference between the display timepoint of said first display starting point picture and the display timepoint of said first display terminating point picture to said storagetime; verifying that continuous display of said first displayterminating point picture and said second display starting point pictureis possible if said time difference is not less than said storage time;and verifying that continuous display of said first display terminatingpoint picture and said second display starting point picture is notpossible if said time difference is less than said storage time.
 52. Thecontinuous reproduction possibility verifying apparatus for encoded dataaccording to claim 50 wherein said encoded data is obtained on encodingusing the MPEG (Moving Picture Experts Group) system.